Effects of climate change on the biodiversity of the Arctic

May 7, 2012, 1:05 pm
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This is Section 10.4 of the Arctic Climate Impact Assessment
Lead Author: Michael B. Usher; Contributing Authors:Terry V. Callaghan, Grant Gilchrist, Bill Heal, Glenn P. Juday, Harald Loeng, Magdalena A. K. Muir, Pål Prestrud

This section examines how climate change might affect the biodiversity of the Arctic. The effects are grouped into six categories: potential changes in the ranges of species and habitats (section 10. 4. 1); changes in their amounts, i.e., the extent of habitats and population sizes (sections Changes in the extent of arctic habitats, below, and Effects on migratory species and their management, below); possible genetic effects (section 10. 4. 4); changes in migratory habits (section 10. 4. 5); likely problems from non-native species (section 10. 4. 6); and implications for the designation and management of protected areas (section 10. 4. 7).

The discussions should be read alongside the appropriate sections of Chapters 7 (tundra and polar desert ecosystems), 8 (freshwater ecosystems),and 9 (marine systems), which also include analyses of the effects of climate change. This section should also be read alongside the appropriate sections of Chapters 11 (wildlife conservation and management) and 14 (forests and agriculture). In this chapter analyses are oriented toward the conservation of arctic genes, arctic species, and arctic ecosystems.

Changes in distribution ranges (10.4.1)

In a warming environment it is generally assumed that the distribution range of a species or habitat will move northward, and that locally it will move uphill. Although such generalizations may be true, they hide large differences between species and habitats, in terms of how far they will move and whether they are actually able to move.

Some of the earlier studies were undertaken in Norway and investigated the "climate-space" then occupied by a few communities and plant species. The "climate-space" comprised two factors – altitude and distance inland[4]. Figure 10.11 shows the effect of a probable climate change scenario on the distribution of blueberry (Vaccinium myrtillus) heaths. The heath is predicted to move uphill, with its mean altitude changing from about 760 m to about 1160 m. The questions for the conservation of this type of heathland are whether all heaths below 700 m will cease to exist (and how quickly this will happen) and whether the heaths can actually establish at altitudes of between about 1300 and 1600 m. Similar studies for other plant species generally predict that they will move to occupy a climate-space that is at a higher altitude and further inland[5].

 

caption Fig. 10.11. A correlative model showing the current (black squares) and predicted (shaded purple) range of Vaccinium heaths in Norway. The grid cells represent steps of 100 m in altitude on the vertical axis and 5 km distance from the sea on the horizontal axis. The model is derived from the then most probable scenario of climate change in Norway,i. e. ,a 2° C increase in July temperatures and a 4° C increase in January temperatures[1].

 

Norway spruce (Picea abies) presently occurs throughout Fennoscandia and Russia, more or less as far north as the shore of the Arctic Ocean. If winter temperatures rise by 4°C,the distribution range projected for Norway spruce virtually halves, with the majority of the southern and southwestern populations disappearing[6]. Owing to the barrier caused by the Arctic Ocean, Norway spruce cannot expand its distribution northward, and so is squeezed into a smaller area. Holten and Carey[7] also projected the distribution of beech (Fagus sylvatica),a tree whose present distribution is more southern. They forecast that this species will spread northward into the Arctic, and may potentially replace the spruce in some of the more coastal areas. The distribution range of the beech thus expands as it shifts north and moves into the Arctic, there being apparently no barriers to its expansion (except perhaps for the size of its seed which makes dispersal more difficult).

In modeling changes in distribution ranges,attempts are made to identify the "climate-space" which a species or habitat currently occupies, and then to identify where that climate-space will occur under scenarios of climate change, for example in 2050 or 2100. Such models assume that the species or habitat currently occupies its optimal climate-space, and that the species or habitat will be able to move as the climate changes. This brings up a range of questions about the suitability of areas for moving through and of barriers,such as mountains for terrestrial species and habitats, or the difficulty of moving from lake to lake, or river to river, for freshwater species. Such models have been used to project what might happen to species on nature reserves [8], in mountain environments[9], and to the species of the major biomes isolated on nature reserves[10]. Dockerty et al.[11] predicted that the relict arctic and boreo-arctic montane species in temperate regions are all likely to have a decreased probability of occurrence in the future.

Arctic species and habitats are thus likely to be squeezed into smaller areas as a result of climate change. However, there are some caveats. Cannell et al.[12], exploring interactions with pollutant impacts (the CO2 fertilization effect and nitrogen deposition), concluded that the movement of plant species may be less than expected,but that the stress-tolerant species, including those characteristic of the Arctic, are likely to be lost. Oswald et al.[13] also explored possible changes in plant species in northern Alaska, and concluded that the responses of species and habitats are likely to be heterogeneous. The continued northward push of the more southern species and habitats has been outlined by Pellerin and Lavoie[14] in relation to changes in ombrotrophic bogs due to forest expansion. It is these individualistic responses to climate change[15], by species and habitats,which make prediction difficult. Individualistic responses appear to be the norm rather than the exception for plants and invertebrate animals[16].

The individualistic responses of species may produce novel effects. This is illustrated using the example of a simple and hypothetical community with a broadly similar abundance of three species: A, B, and C (community A+B+C). Under a climate change scenario with species moving northward, if species A moved rapidly,species B moved more slowly,and species C hardly moved at all, this could result in a community dominated by species A with species B as a sub-dominant (community A+b) in the north and a community dominated by species C with species B as a sub-dominant (community C+b) more or less where A+B+C used to occur. It is possible that neither A+b nor C+b would be recognized as communities, and so, in the geographical contraction of A+B+C, two new communities – A+b and C+b – had arisen,both of which were novel. Climate change could thus give rise to some new habitat types, and although this might not change the overall biodiversity of the Arctic at the species level, there could be changes to biodiversity at the habitat level.

Current distribution ranges of plants and animals in the marine environment depend upon the ocean currents as well as on the extent of the sea-ice cover at different times of the year. With the projected decrease in sea-ice cover and the more northerly position of the ice edge, the distribution of the algae, phytoplankton, invertebrates, and fish will also change. An analysis of the effects of climate change on marine resources in the Arctic[17] left much in doubt, stating that "the effects of climate variation on some Bering Sea fish populations are fairly well known in terms of empirical relationships but generally poorly known in terms of mechanisms". The authors proposed a program of research to help predict the effects of climate change on the commercially-exploited fish stocks and more widely on marine biodiversity as a whole.

 

caption Fig. 10. 12. A representation of extent of understanding and the quality or quantity of data when applied to modeling problems. For the majority of potential applications in conservation the level of understanding of the system is low and the quantity of data small, and so the modeling would fall in the lower left corner of Zone 4[2].

 

The lack of knowledge on this topic was addressed by Starfield and Bleloch[18]. They presented a simple model of the context within which most conservation work could be undertaken (Fig. 10. 12). Conservation generally has little understanding of the system to be conserved, and managers have poor data upon which to build models. The conservation of biodiversity falls in zone 4. This is the zone where statistical models are most helpful, indicating expectations with some probability attached and often very wide confidence limits.

What are the implications for conservation? The most detailed assessment of changes in distribution ranges of species and ecosystems in relation to conservation are probably the studies on national parks and other conservation areas in Canada[19]. The large scale of biomes and environmental conditions in Canada facilitate the definition of spatial patterns by models with a grid resolution of 0. 5° latitude by 0. 5° longitude. The studies of 36 national parks and other designated conservation areas involved the application of two global vegetation models (BIOME3 and MAPSS) which represent the effects of enhanced CO2 on nine or ten biome types consistent with IPCC analysis. The different number of biomes is because BIOME3 combined boreal and taiga/ tundra biomes which were separated in MAPSS. Five general circulation models (three equilibrium models: UKMO, GFDL-R30, and GISS; two transient models: HadCM2 and MPI-T106) were applied, providing some direct cross-reference to the present assessment.

 

caption Fig. 10. 13. The present MAPSS vegetation distribution in Canada’s national parks. Nine vegetation zones are shown,excluding the permanent ice in the north (reproduced with permission from Daniel Scott,University of Waterloo,Canada).

 

A northward movement of the major biomes was projected in all five scenarios, changes in the dominant biomes of tundra, taiga/tundra, and boreal conifer forest were particularly clear (compare Fig. 10. 13, which shows present conditions, with Fig. 10. 14, which shows two projections for the northerly movement of the Canadian vegetation zones). As is the case for the ACIA-designated climate models (see Chapter 4), although the trends were similar between models, the actual values and local spatial patterns showed considerable variation. Regardless of the vegetation and climate change scenarios used,the potential for substantial changes in biome representation within the national parks was shown repeatedly. At least one non preexisting biome type appeared in 55 to 61% of parks in the MAPSS-based scenarios and 39 to 50% in the BIOME3-based scenarios. Representation of northern biomes (tundra, taiga/ tundra, and boreal conifer forest) in protected areas was projected to decrease due to the overall contraction of these biomes in Canada. Projections for the southern biomes were more variable but their representation in protected areas generally increased.

 

caption Fig. 10. 14. The projected MAPSS vegetation distribution in Canada’s national parks using two scenarios of climate change. Although the details of these two projections differ, they both demonstrate the northward movement of vegetation zones relative to current conditions (reproduced with permission from Daniel Scott,University of Waterloo,Canada).

 

The seven arctic national parks range in size from Vuntut in Yukon Territory at 4345 km2 to Quttinipaaq (formerly Ellesmere Island) at 37775 km2 in Nunavut. The parks cover a range of conditions from high arctic polar desert and glaciers to taiga, extensive wetlands, coastal areas, lakes, and rivers. They also contain, and were often designated to conserve, a variety of species and populations; for example, they contain one of the greatest known musk oxen (Ovibos moschatus) concentrations, calving grounds for Peary caribou (Rangifer tarandus pearyi), migration corridors and staging areas, one of the largest polar bear denning areas, spawning and over-wintering sites for Arctic char, considerable species richness with over 300 plant species in one area, plus important historical, cultural, and archaeological sites and unique fossils from Beringia. Some of the significant impacts of climate change within the arctic national parks are outlined in Table 10. 7.

Changes in the extent of arctic habitats(10.4.2)

The previous section showed that distribution ranges of many arctic habitats are likely to decrease with climate change and that this generally implies a reduction in the overall extent of the habitat. The response of each habitat is likely to be individualistic[20], and to depend upon the dynamics of the populations and communities, as well as on a range of species interactions such as competition, predation, parasitism, hyperparasitism, and mutualism. Habitat extent will depend upon the individualistic responses of the component species, and these in turn will depend upon the physiological responses of the individuals that form those species populations (see section 10. 4. 3).

In the marine environment far less is known about the potential effects of warmer temperatures, increased atmospheric CO2 concentrations, and increased irradiance by ultraviolet-B (UV-B) on the species populations and habitats. A review of marine nature reserves by Halpern and Warner[21] showed that changes in population sizes and characteristics can be fast. Compared with undesignated areas, their study indicated that the average values of density, biomass, organism size, and diversity all increased within one to three years of designation. These rapid responses, the result of protection through conservation designation, indicate that marine organisms and marine habitats have the potential to respond quickly to changed environmental conditions.

 

Table 10. 7. Potential impacts of climate change on the arctic national parks and other protected areas[22].

Impact

Effects of impact

Northward treeline extension

Up to 200–300 km movement in the next 100 years (where movement is not impeded by soil condition)

Increased active layer and permafrost thawing

May extend northward by 500 km, causing altered drainage patterns

Sea-level rise

Variable, either moderated by isostatic rebound or exacerbated by subsidence

Reduced sea- and lake-ice seasons

Altered sea mammal distributions (especially for polar bears and ringed seals), as well as more northerly distribution of ice-edge phytoplankton blooms, zooplankton, and fish

Increased snowpack and ice layers

Reduced access to browse for ungulates

Greater severity and length of insect seasons

Increased harassment of ungulates and potential for pest outbreaks in boreal forests

Altered migration patterns

Diminished genetic exchange amongarctic islands

Altered predator–prey and host–parasite relationships

Changes in species abundance, and potentially the establishment of novel interactions between pairs of species

Change will occur, and in general it appears that arctic habitats are likely to have smaller population sizes within smaller distribution ranges. What will replace them? Habitats that currently occur in the sub-Arctic or in the northern boreal zone are likely to move northward, and their responses to climate change are likely to be individualistic. So it is possible that habitats currently south of the Arctic might migrate northward and occur “naturally”within the Arctic, as for example with the northward movement of beech forest (section 10. 4.1).

This will make it difficult to establish, if indeed there is a distinction, whether species and habitats of the Arctic in the future are native or non-native (see section 10. 4. 6). Owing to the different responses of habitats and species, it is likely that novel species assemblages will occur in the future, being habitat types that are currently unknown or not envisaged. Thus, the current habitat classifications are likely to have to change as novel habitat types evolve in response to rapid climate change. This has considerable implications for species and habitat conservation and for management today, and may lead to alterations in the priorities for biodiversity conservation in the future. While the name of a species is more or less stable, and so easily incorporated into legislative frameworks (i. e. , appended lists of protected species), a habitat’s name and description is less stable, implying a need for periodic reviews of legislative frameworks.

Changes in the abundance of arctic species (10.4.3)

As sections 10. 4. 1 and 10. 4. 2 imply, it is the species composition of an area that will change, forcing changes to the communities in which they occur. The individualistic responses of the species[23] will depend upon the dynamics of the species populations, the competitive or mutualistic interactions between species, and the biochemical and physiological responses of the individuals.

Biochemistry and physiology are fundamental to how an individual responds to its environment and to changes in that environment. Rey and Jarvis[24] showed that young birch (Betula pendula) trees grown in an atmosphere with elevated CO2 levels had 58% more biomass than trees grown in ambient CO2 concentrations. They also found that the mycorrhizal fungi associated with the roots of the experimental trees differed; those grown in elevated CO2 levels were late successional species, while those grown in ambient CO2 levels were the early successional species. This showed the complexity of understanding the effects of climate change on the conservation of biodiversity. Normally, with regenerating birch trees, the whole successional suite of fungi would be expected to occur on the young trees’ roots as they emerge from the seed, establish themselves, grow, and then mature. Does the work of Rey and Jarvis[25] imply that more attention needs to be given to protecting the early successional mycorrhizal species? They will clearly be needed in the ecosystem if climate cools or CO2 levels fall in the future.

Other physiological studies have detected a 4 to 9% thickening of the leaves of lingon berry (Vaccinium vitis-idaea) under enhanced UV-B radiation, whereas the deciduous blueberry and bog blueberry (V. uliginosum) both had 4 to 10% thinner leaves under similar conditions[26]. Growth of the moss Hylocomium splendens was strongly stimulated by enhanced UV-B radiation, as long as there was additional water, whereas the longitudinal growth of the moss Sphagnum fuscum was reduced by about 20%. Björn et al.’s[27] results for lichen growth under enhanced UV-B radiation were variable, leading them to conclude that "it is currently impossible to generalize from these data". They also investigated the decomposition of litter from Vaccinium plants grown under normal conditions and under conditions of enhanced UV-B radiation. Litter from the V. uliginosum plants treated with UV-B radiation had a decreased cellulose content, a reduced cellulose/lignin ratio, and increased tannins compared to the control litter, and so was more resistant to decomposition. Slower decomposition was also observed for V. myrtillus litter. Björn et al.[28] did not investigate the palatability of the leaves to invertebrate animals. Moth larvae, particularly those in the family Geometridae (the “loopers”or “spanworms”), are a large component of the diet of many passerine birds in the boreal forest and near the forest/tundra margin. If the larval population densities are reduced due to a lack of palatability of the leaves on which they feed, the effects of UV-B radiation could be far-reaching on the below-and-above-ground food webs of the terrestrial Arctic.

Changes in phenology, the time of year when events happen, will also affect the size of populations. A number of studies have already shown that vascular plants are flowering earlier, insects (especially butterflies) are appearing earlier in the year, some birds are starting to nest earlier in spring, amphibians are spawning earlier, and migratory birds are arriving earlier (see a review by Usher[29]). Some of these phenological observations are beginning to be used as indicators of the effects of climate change on biodiversity, although most studies are just recording data on the changes in species populations in the earlier part of the year (usually spring) and do not record data for the end-of-summer changes that could be affecting plant growth rates in the autumn or autumnal flight periods for species of insect. The important ecological impact of phenology concerns how changes will affect interactions between pairs of species. If one species changes its phenology more than another, will this then increase or decrease the effects of competition, herbivory, predation, parasitism, etc.? If synchrony occurs, and the organisms become less synchronous, this could have considerable effects on population sizes and biodiversity.

In the marine environment, seabirds show strong preferences for regions of particular sea surface temperatures (SSTs)[30]. Some seabird populations have been found to respond to long-term climatic changes in the North Atlantic Ocean[31], the North Pacific Ocean[32], and Antarctica. Although global SSTs are generally increasing, this long-term trend is superimposed on cyclical patterns created by climatic oscillations, such as the North Pacific, North Atlantic, and Arctic Oscillations[33]. These oscillations cause periodic reversals in SST trends, two of which have occurred since 1970 in the Northern Hemisphere; from 1970 much information has been accumulated on seabird population trends in the circumpolar Arctic[34].

To examine the effect of SST changes on seabird populations at a global scale, data on population changes throughout the distribution ranges of the common guillemot or murre (Uria aalge) and Brünnich’s guillemot or thick-billed murre (U. lomvia) were examined to document how they changed in response to climate shifts, and potential relationships with SSTs[35]. Both species breed throughout the circumpolar north from the high Arctic to temperate regions, although Brünnich’s guillemots tend to be associated with colder water than common guillemots and are the dominant species in the Arctic[36].

The analysis showed that positive population trends occurred at guillemot colonies where SST changes were small, while negative trends occurred where large increases or large decreases in SST occurred. Highest rates of increase for the southerly species, the common guillemot, occurred where SST changes were slightly negative, while increases for the arctic-adapted Brünnich’s guillemot were most rapid where SST changes were slightly positive. These results demonstrate that most guillemot colonies perform best when temperatures are approximately stable, suggesting that each colony is adapted to local conditions[37]. This study also demonstrates how seabirds respond to changes in climatic conditions in the Arctic overlarge temporal and spatial scales.

A study on the Atlantic puffin in the Lofoten Islands, northern Norway, has shown that sea temperatures from March through July (which is the first growth period for newly hatched Atlantic herring) and the size of herring in the food intake of adult puffin together explain about 84% of the annual variation in fledging success of puffin chicks[38]. Although there are relatively few data for the marine environment, what there are(especially for seabirds) indicate reduced population sizes for many of the marine wildlife species of the Arctic, and so conservation activity must aim to ameliorate such declines. Protected areas are an important aspect of such activity and are discussed further in section 10. 4. 7.

Changes in genetic diversity (10.4.4)

Little attention had been paid to genetic diversity, despite it being one of the major themes in the Convention on Biological Diversity. For example, Groombridge’s[39] book on biological diversity had 241 pages on species diversity, 80 pages on the diversity of habitats, but only 6 pages on genetic diversity. Similarly, Heywood’s[40] Global Biodiversity Assessment had only 32 pages on the subject of "genetic diversity as a component of biodiversity" of its total of 1140 pages.

The reason for this discrepancy is because species tend to be tangible entities and many are easily recognizable. The species concept does not work well, however, for the single-celled forms of life, which often live in soils or sediments under freshwater or the sea, where the genetic variability is often more important than the species itself. Habitats are also recognizable, often on the basis of their species, but present complications because they tend to merge into one another. Compared with these tangible entities, genetic variability is often not recognizable and can only be detected by sophisticated methods of analysis using molecular techniques. Of the millions of species that exist, very little is known about their genetic diversity except for a few species of economic importance, a few species that are parasites of people or their domestic stock, and a few other species that geneticists have favored for research (e. g. , the Drosophila flies). As in all other parts of the world, relatively little is known about the genetic variability of species that occur in the Arctic.

What then can be done to conserve the Arctic’s genetic diversity? On the basis that natural selection requires a genetic diversity to operate, conservation practice should aim to find a surrogate for the unknown, or almost unknown, genetic diversity. This is best done by conserving each species over as wide a distribution range as possible and in as many habitats as possible. This ensures maximum geographical and ecological variability, assuming that local adaptation of species represents different genotypes. Attempting to map population genetics to landscape processes is relatively new[41] and has been termed “landscape genetics”. Manel et al.[42] stated that it "promises to facilitate our understanding of how geographical and environmental features structure genetic variation at both the population and individual levels, and has implications for. . . conservation biology". At the moment it must be assumed that the geographical and environmental features have structured the genetic variation, and this assumption must be made before the links can be proved. How this variability has actually arisen is unclear.

Throughout continental Europe, a continuous post-glacial range expansion is assumed for many terrestrial plant and animal species. This has often led to a population structure in which genetic diversity decreases with distance from the ancestral refugium population[43], and so northern populations are often genetically less diverse than their southern counterparts[44].

Among discontinuously distributed species, such as those living on remote islands, this pattern can be obscured by differences in local effective population sizes. For example, considerable genetic diversity exists among populations of common eider ducks (Somateria mollissima) nesting throughout the circumpolar Arctic. Historical and current processes determining phylogeographic structure of common eiders have recently been reconstructed, based on maximum parsimony and nested clade analysis[45]. Five major groups (or “clades”) have been identified; the three most different include common eiders from Alaska, Svalbard, and Iceland. The remaining two include eider populations from the eastern Canadian Arctic and West Greenland, and from northwest Europe.

Nested clade analysis also suggests that the phylogeographic patterns observed have a strong historical pattern indicating past fragmentation of eider populations due to glacial events. Following the retreat of the glaciers, eiders surviving in refugia expanded to re-colonize their range, and populations apparently remixed. These refugial populations occurred across Arctic Canada and Greenland[46], and apparently in a single refugium in northwest Europe[47]. The oldest population split was estimated between Pacific eiders and birds that colonized the western Canadian Arctic islands about 120 000 years ago after the retreat of ice sheets in the previous glacial maximum. In North America, this was likely to have been followed by a second expansion that began in warmer periods about 80 000 years ago from Alaska eastward across the Palearctic to establish populations in the eastern Canadian Arctic and West Greenland. In Europe, genetic analyses suggest that common eiders underwent a post-glacial range expansion from a refugium in Finland, north and west to the Faroe Islands and subsequently to Iceland. Despite this relatively recent mixing of haplotypes, extant populations of common eider ducks are strongly structured matrilineally in the circumpolar Arctic. These results reflect the fact that current long--distance dispersal is limited and that there is considerable philopatry of female eiders to nesting and wintering areas[48].

In contrast to common eider ducks, king eider ducks (Somateria spectabilis) show a distinct lack of spatial genetic structure across arctic North America[49]. In the western Palearctic, the king eider has been delineated into two broadly distributed breeding populations in North America, in the western and eastern Arctic, on the basis of banding (ringing) data[50] and of isotopic signatures of their diet while on wintering grounds[51]. These studies indicated the use of widely separated Pacific and Atlantic wintering areas. Despite this, recent studies of microsatellite DNA loci and cytochrome b mitochondrial DNA show small and non-significant genetic differences based on samples from three wintering and four nesting areas in arctic North America, Russia, and Greenland[52]. Results from nested clade analysis and coalescent-based analyses suggest historical population growth and gene flow that collectively may have homogenized gene frequencies. However, the presence of several unique mtDNA haplotypes among birds wintering in West Greenland suggested that gene flow may now be more limited between the western and eastern arctic populations than in the past[53]; this would be consistent with recent banding data from eastern Canada and West Greenland[54].

Collectively, these two examples of closely related duck species illustrate how climatic events can influence the genetic structure of arctic species over time. They also show how historical periods of isolation, combined with little gene flow currently (matrilineally, at least), have contributed to maintain genetic diversity. However, the fact that the common and king eider differ so markedly in their degree of genetic diversity throughout the circumpolar Arctic, despite sharing many ecological traits, suggests that the effects of more rapid climate change on genetic diversity may be difficult to predict.

There are at least three features of this genetic variability that need to be considered in the conservation of the Arctic’s biodiversity. First, the genetic structure of a species at the edge of its range, where it is often fragmented into a number of small and relatively isolated populations, is often different from that at the center of the range, where populations can be more contiguous and gene flow is likely to be greater. It is these isolated, edge-of-range populations that are possibly undergoing speciation, and which might form the basis of an evolution toward different species with different ecologies in the future.

Second, hybridization can be both a threat and an opportunity. Although arctic examples are rare, it can be a threat where two species lose their distinctive identities, as is happening with the introduction of Sika deer (Cervus nippon) into areas where red deer (C. elaphus) naturally occur. This is one of the potential problems with the introduction into the Arctic of non-native species (section 10. 4. 6). Hybridization can also be an opportunity. The hybrid between the European and American Spartina grasses doubled its number of chromosomes and acts as a newly evolved species in its own right.

Third, there are suggestions[55] that the genetic variability of populations is important in maintaining the full range of ecosystem services. Although this concept is little understood, it is intuitively plausible because, as factors in the environment change, individuals of differing genetic structure may be more or less able to fulfill the functional role of that species in the ecosystem. Thus, with a variable environment, the ecosystem needs species whose individuals have a variable genetic makeup.

Although little is known about genetic variability, a geographically spread suite of protected areas, encompassing the full range of habitat types, is probably the best conservation prescription for the Arctic’s biodiversity that can currently be made. It should be appropriate for conserving the biodiversity of habitats and species, and is probably also appropriate for conserving genetic biodiversity.

Effects on migratory species and their management (10.4.5)

Migration was briefly addressed in sections 10. 2. 6 and 10. 3. 2, and the eight major international flyways for shorebirds breeding in the Arctic are shown in Figure 10. 4. Migration is a cold and ice avoidance strategy used by birds, marine mammals, and fish. Although some species of insect also migrate, it is uncommon for the milkweed butterfly (Danaus plexippus), well known for its migrations through North America, to migrate in the spring and early summer as far north as the Canadian Arctic.

The goose species of the western Palearctic region provide good examples of migratory species that have been the subject of considerable research and conservation action[56]. Of the 23 populations, five populations of greylag goose (Anser anser anser and A. a. rubirostris) do not nest in the Arctic; neither do the two populations of Canada goose (Branta canadensis) which are not native to the region. The remaining 16 populations of seven species (11 subspecies) are listed in Table 10. 8. There are a variety of flyways, some moving southeast from the breeding grounds in northeast Canada, Greenland, and Iceland, and others moving southwest from the breeding grounds in the Russian Arctic, both into Western Europe. The three populations of barnacle goose (Branta leucopsis) can be used as an example.

The examples demonstrate a number of features of migratory populations and their conservation. The geese require sufficient food resources to make two long journeys each year. The summer feeding grounds in the Arctic and the winter feeding grounds in temperate Europe provide the majority of the food requirements. However, while on migration, the geese need to stage and replenish their energy reserves. In years when winter comes early and Bjørnøya is iced over before the geese arrive, it is known that many are unable to gain sufficient energy to fly on to Scotland and there can be very heavy mortality, especially of that year’s young. Although the three populations appear from the brief descriptions in Box 10. 1 to be geographically isolated from each other, there is a very small amount of mixing between these populations, and so gene flow is probably sufficient for this one species not to have sub-speciated.

The examples also demonstrate that conservation efforts need to be international. For each of the three populations, protection is required for parts of the year in the breeding grounds, in the wintering grounds, and in the staging areas. Conservation action needs to be taken wherever the geese land. The fact that there is some straying from the main flight paths implies that conservation is required all along these migration routes. In Europe, the Bonn Convention aims to provide such an instrument for the conservation of migratory species; this could form a model for all migratory species, including those that use the Arctic for part of their life cycle.

Climate change could affect these species through changes in their habitats. For the Greenland nesting population it would be possible for their breeding grounds to move northward because there is land north of the current breeding range. This could hardly happen for the populations breeding on Svalbard and in Russia because there is very little ground north of the current breeding areas (just the north coast of Svalbard and the north of Novaya Zemlya). Because many of the wintering grounds are managed as grasslands for cattle and sheep grazing, it is possible that these may change less than the breeding grounds. The staging areas are also likely to change, and it is possible that the distance between breeding and wintering grounds might become longer, requiring more energy expenditure by the migrating birds. This leaves a series of unknowns, but at present these goose populations are increasing in size, are having an economic impact on the wintering grounds, and have raised what Usher[57] has termed "the dilemma of conservation success". This is the problem of reconciling the interests of the local people with the need to conserve species that the people either depend upon harvesting or that damage their livelihoods.

Table 10. 8. The sixteen goose populations that nest in the Arctic and overwinter in the western Palearctic. The data were extracted from Madsen et al.[58].

 

 

Breeding area

Wintering area

Taiga bean goose

Anser fabalis fabalis

Scandinavia and Russia

Baltic

Tundra bean goose

Anser fabalis rossicus

Russia

Central and Western Europe

Pink-footed goose

Anser brachyrhynchus

Iceland and Greenland

Great Britain

Pink-footed goose

Anser brachyrhynchus

Svalbard

Northwest Europe

White-fronted goose

Anser albifrons albifrons

Russia

Western Europe

Greenland white-fronted goose

Anser albifrons flavirostris

West Greenland

British Isles

Lesser white-fronted goose

Anser erythropus

Scandinavia and Russia

Central and southeast Europe

Greylag goose

Anser anser anser

Iceland

Scotland

Greylag goose

Anser anser anser

Northwest Europe

Northwest and southwest Europe

Barnacle goose

Branta leucopsis

East Greenland

British Isles

Barnacle goose

Branta leucopsis

Svalbard

Scotland and northern England

Barnacle goose

Branta leucopsis

Russia and the Baltic

Northwest Europe

Dark-bellied brent goose

Branta bernicla bernicla

Russia

Western Europe

Light-bellied brent goose

Branta bernicla hrota

Northeast Canada

Ireland

Light-bellied brent goose

Branta bernicla hrota

Svalbard

Northwest Europe

Red-breasted goose

Branta ruficollis

Russia

Black Sea

Effects caused by non-native species and their management  (10.4.6)

Biological invasions have fascinated ecologists for well over 50 years[59]. The many problems caused by non-native species are becoming more apparent, and the World Conservation Union (IUCN) identifies them as the second most important cause of loss in global biodiversity (the primary reason being loss and fragmentation of habitats). A word of caution is, however, needed with language. Why a species is geographically where it is currently found cannot always be determined; if it is known to be there naturally, it is generally referred to as "native". If it has been brought in from another geographical area by human agency, either intentionally or unintentionally, it is referred to as "non-native" (Usher[60] discussed these distinctions and the gradations between them). The term "non-native" is essentially synonymous with "alien", "exotic", and "introduced", all of which occur in the literature. Williamson[61] described the "10:10 rule", suggesting that 10% of species introduced to an area would establish themselves (i. e. they do not die out within a few years of introduction, and start to reproduce) and that 10% of these established species would become "pests". While this rule seems reasonably true for plants, it seems to underestimate the numbers of vertebrate animals that become problematic[62]. It is this 1% (10% of 10%) of species that are introduced, or rather more for vertebrate animal species, which can be termed "invasive".

To date, the Arctic has escaped the major problems that invasive species have caused in many other parts of the world. During the 1980s there was a major international program on the ecology of biological invasions. The synthesis volume[63] does not mention the Arctic (or the Antarctic), although global patterns of invasion into protected areas indicated that the problems diminished with latitude north or south of the regions with a Mediterranean climate[64].

In terrestrial ecosystems, climate change is very likely to mean that more species will be able to survive in the Arctic. It is arguable whether new species arriving in the Arctic can be classified as "native" or "non-native" when the rapidly changing climate is anthropogenically driven. However, with a changing climate new species will very probably arrive in the Arctic, some of which will establish and form reproducing populations. Although there is no obvious candidate for a non-native species to be invasive in the Arctic, it needs to be remembered that at least 1% of species introduced into the Arctic are likely to become invasive. At present there are no means of determining the major risks, but the introduction of disease organisms, for wildlife and people, is a distinct possibility.

In the boreal forests, the insects, as a group, pose the most serious challenge because of their ability to increase rapidly in numbers and because of the scarcity of effective management tools. From past experience, it is probable that many forest-damaging insects have the potential to appear at outbreak levels under a warmer climate and increased tree stress levels, but this has not been observed to date. Two examples demonstrate the risks. First, the bronze birch borer (Agrilus anxius) has been identified as a species that can cause severe damage to paper birch (Betula papyrifera), and maybe effective in limiting the birch along the southern margin of its distribution[65]. It is currently present at relatively low levels in the middle and northern boreal region of North America. Second, an outbreak of the Siberian silkworm (Dendrolimus sibiricus) in west Siberia from 1954 to 1957 caused extensive tree death on three million hectares of forest. Movement of outbreak levels northward would considerably alter the dynamics of Siberian forests.

There are similar concerns in the freshwater environment. In much of northern Europe and northern America, it is the introduction of fish species that cause most problems. For example, in Loch Lomond in Scotland the invasive ruffe (Gymnocephalus cernuus) eats the eggs of an arctic relict species, the powan (Coregonus lavaretus), thereby threatening this species in one of its only British habitats[66]. Similarly, in North America the invasion of the Great Lakes by the lamprey (Petromyzon marinus), first seen in Lake Erie in 1921, led to the collapse of a number of fisheries following its establishment and first known breeding in the 1930s. For example, the trout fishery in Lake Michigan was landing about 2600 tonnes of fish each year between 1935 and 1945, but this dropped to 155 tonnes by 1949 when the fishery essentially ended[67]. Although these examples are outside the Arctic, they highlight potential problems with non-native fish species as arctic rivers and lakes become warmer. There are also potential problems with fish that escape from fish farms and enter the natural environment and breed with native fish stock. The genetic effects of this interbreeding can be profound, altering the behavior of the resulting fish stock, as has been found with Atlantic salmon (Salmo salar) in Norway.

In the marine environment one of the major potential problems is the discharge of ballast water. With thinning of the sea ice and the opening up of the Arctic Ocean to more shipping for more of the year, the possibility of the introduction of non-native species is greater and the environmental risks are increased. Analyses of ballast water have shown that it can contain a large number of different species of marine organisms, including marine algae and mollusks that are potentially invasive. Also, ballast water has occasionally been found to contain organisms that could be pathogenic to people. Regulating discharges of ballast water is not easy, nor is its enforcement always possible, but to prevent the threat of invasive marine organisms it is essential that international agreements regulate such discharges in coastal waters and on the high seas of the Arctic.

The effects of introduced Arctic foxes on seabird populations is an example that links the marine and terrestrial environments. Seabirds commonly nest on offshore islands, in part to avoid terrestrial predators to which they are vulnerable, both to the loss of eggs and chicks and to direct predation on adults. Several seabird populations have declined when mammalian predators were accidentally or intentionally introduced to nesting islands[68]. Arctic foxes were intentionally introduced for fur farming in the late 1800s and early 1900s on several of the Aleutian Islands of Alaska. Before these introductions, the islands supported large populations of breeding seabirds and had no terrestrial predators. Although most fox farming ended prior to the Second World War, the introduced animals persisted on many islands, preying on breeding seabirds at rates affecting their population sizes[69]. Evidence from southwestern Alaska[70], and comparisons of islands with and without foxes in the Shumagin Islands[71], suggest it is likely that foxes are responsible for the reduced seabird population sizes on islands supporting foxes. Those species nesting underground, in burrows or in rock crevices, were less affected[72].

Foxes have recently been eradicated from several islands[73] and the responses of seabird populations have been dramatic. Pigeon guillemot (Cepphus columba) populations began to increase within three to four years following fox removal at Kiska Island and 20-fold increases occurred in guillemot numbers at Niski-Alaid Island within 15 years of fox removal[74]. The introduction of Arctic foxes to the Aleutian Islands, and their influence on native seabird species, provides a dramatic example of how the intentional introduction or movement of species can influence arctic biodiversity.

The report by Rosentrater and Ogden[75] contained the cautionary note "presently, the magnitude of the threat of invasive species on Arctic environments is unclear: however, the potential impacts of this threat warrant further investigation and precautionary action on species introductions, especially since climate change is expected to result in the migration of new species into the region". The risk to the environment and to biodiversity of intentionally introducing any non-native species into the Arctic must be established before the species is introduced. Experience worldwide indicates that it is often too late if the risk is assessed after the introduction; it might then also be too late to control the spread and effects of the invasive species. The precautionary action is to stop the arrival of the invasive species in the first place because its later eradication may be impossible, and even if possible worldwide experience shows that it is likely to be extremely expensive.

Effects on the management of protected areas (10.4.7)

Establishment of protected areas has been a core activity of conservation legislation throughout the world. The concept is implemented in different ways by different national governments, with differing degrees of success, as is clear from reviews of international activities (e. g. , IUCN[76]). This section reviews the underlying ecological concepts related to the conservation of biodiversity and the potential effects of climate change.

Reviews by CAFF[77] showed that much progress has been made in designating protected areas in the Arctic, but that further progress is needed, especially in the marine environment. Halpern and Warner[78] indicated that marine reserves are very effective at conserving biodiversity, and Halpern[79] considered that marine protected areas need to be large in extent. In the terrestrial and freshwater environments, some of the largest protected areas worldwide occur in the Arctic. Few studies explore whether such protection is achieving its stated aims.

In general the establishment of protected areas has a scientific foundation. As Kingsland[80] stated "its goal is to apply scientific ideas and methods to the selection and design of nature reserves and to related problems, such as deciding what kinds of buffer zones should surround reserves or how to establish corridors to link reserves and allow organisms to move from one area to another. As in other areas of conservation biology, designing nature reserves is a ‘crisis’ science, whose practitioners are driven by an acute sense of urgency over the need to stem the loss of species caused by human population growth". This to some extent misses a vital point: the social sciences are also involved with conservation. Why is it important to conserve biodiversity, why are particular species favored over others, or how do people fit into the conservation framework? Such questions are not addressed here, despite their importance to the local communities of the Arctic (section 10. 2. 7); this section focuses on the scientific bases of conservation.

Three main facets of ecological thinking have affected the design of potential protected areas. The concepts of island biogeography, of habitat fragmentation, and the establishment of metapopulations (and of corridors) are not unrelated and can all impact upon protected areas in a changing climate.

The concept of island biogeography[81] includes the idea that the number of species on an island is dynamic, representing the equilibrium between the arrival of new species and the extinction of existing species. Larger islands would have greater immigration rates, and possibly smaller stochastic extinction rates, than small islands, and hence the equilibrium number of species would be greater. Similarly, distant islands would have smaller immigration rates than similarly sized islands nearer the source of immigrants, but would probably have similar extinction rates, and so would have fewer species. Using many sets of data for island biota, these concepts are formulated into the empirical relationship:

S = CAz

where S is the number of species on the island, A is the area of the island, and C and z are constants (C represents the number of species per unit area, and z generally takes a value of about 0. 3. This relationship implies that if the island area is increased tenfold, the number of species will about double). Although there have been few island biogeographical studies in the Arctic, Deshaye and Morisset[82] confirmed that larger islands in the subarctic (in the Richmond Gulf, northern Québec, Canada) contain more species than smaller islands.

Island biogeography has thus been used to justify larger rather than smaller protected areas. With climate change, and with arctic wildlife populations and their distribution ranges likely to diminish (sections 10. 4. 1 to 10. 4. 3), use of the precautionary principle would also suggest that larger rather than smaller protected areas should be established.

Fragmentation of ecosystems has been viewed as the “islandization” of habitats. Although fragments cannot be thought of as real islands, the use of island biogeographical concepts tends to apply relatively well[83]. This has led to the formulation of "rules" for the design of protected areas, starting with Diamond[84], but leading to more sophisticated designs as in Fig. 10. 15. Size and shape are the key factors in the design of protected areas, but the inclusion of fragments of natural ecosystems is helpful for biodiversity conservation. Under a changing climate, fragmentation of arctic ecosystems should be avoided. Fragmentation always causes problems[85], even if at some scales it might appear to increase biodiversity[86].

With fragmentation an integral part of modern development, corridors appear to be a useful concept. How does the landscape fit together such that individuals can move from habitat patch to habitat patch? As pointed out by Weber et al.[87], land managers and wildlife biologists must collaborate to determine the patterns of protected areas within the landscape that will be of most benefit to wildlife. Some scientists advocate corridors: Saunders and Hobbs[88] gave a number of examples where corridors appear to work. Others have argued that corridors allow invasive species entry into protected areas, while more recent research calls into question the whole value of corridors. Albeit a beguilingly simple concept, at present neither the value of corridors, nor their lack of value, has been proven. With climate change underway, it is thus best to avoid the necessity for corridors by focusing on larger protected areas and a reduction in the processes leading to habitat fragmentation. This will promote real connectivity, rather than an apparent connectivity, for species and habitats.

However, will the protected areas that exist today, even if they have been located in the best possible place to conserve biodiversity, still be effective in the future with climate change? The answer is probably "no". Designations have been widely used, but are based on assumptions of climatic and biogeographic stability and usually designated to ensure the maintenance of the status quo. Available evidence indicates that these assumptions will not be sustainable during the 21st century. So what can be done to make the network of protected areas more appropriate to the needs of the Arctic and its people?

First, today’s protected areas should encompass land or water that will potentially be useful for biodiversity conservation in the future. This is where models of the changing distribution of species and habitats are useful and where their outputs should be included in the design of protected areas (see the example of the Canadian national parks in section 10. 4. 1). This means that designation should reflect both the present value of the areas for biodiversity as well as the projected future value (the potential value).

Second, boundaries may need to be more flexible. In general, boundaries are lines on maps, and enshrined in legislation, and so are difficult to change. The present practices could be described as having "hard boundaries". An alternative could be that the boundaries change with changes in the distribution of the flora or fauna being protected. That is, over time (probably decades rather than years) the location of the protected areas would shift geographically (this could be described as the protected areas having "soft boundaries"). However, it is important that sociological and developmental pressures do not destroy the value of the protected areas in safeguarding the biodiversity that is their raison d’etre –nothing would be worse than in 50 years time having a network of sites that were protecting very little. More flexible systems of designation, adding areas which are or will become important, and dropping areas that are no longer important, would appear to be one way forward to conserve biodiversity within the Arctic. A system of designations with “soft boundaries” has not yet been tried anywhere in the world, but could become a policy option that is pioneered in the Arctic.

Protected area designations are a major policy and management system for the conservation of biodiversity, as well as for historical and cultural artifacts. Climate change might result in designated communities and species moving out of the designated area; communities and species new to the area will tend to colonize or visit, especially from the south; and assemblages of species without current analogues will form as individual species respond to climate change at different rates and in different ways. It will therefore be necessary to adjust such concepts as "representative communities" and "acceptable limits of change" that are part of the mandate of many national and international designations. The expected changes will include many surprises resulting from the complex interactions that characterize ecosystems and the non-linearity of many responses.

The scientific basis of biodiversity conservation planning in the era of climate change argues against procedures designed to maintain a steady state. There are four general policy options to respond to climate change that have been used in the Canadian national parks (summarized by Scott and Lemieux[89]).

  1. Static management. Continuing to manage and protect current ecological communities and species within current protected area boundaries, using current goals.
  2. Passive management. Accepting the ecological response to climate change and allowing evolutionary processes to take place unhindered.
  3. Adaptive management. Maximizing the capacity of species and ecological communities to adapt to climate change through active management (for example, by fire suppression, species translocation, or suppression of invasive species), either to slow the pace of ecological change or to facilitate ecological change to a new climate adapted state.
  4. Hybrid management. A combination of the three previous policy options.

 

caption Fig. 10. 15. A representation of the biodiversity conservation value of potential protected areas, based on a study of insects in farm woodlands but also applicable to other habitats and other taxonomic groups[3]. The scaling should change to reflect the larger areas prescribed for the Arctic. Habitats are in black and habitat fragments are small white circles. Linear features, such as small rivers, are represented by straight lines.

 

It is likely that adaptive management will be the most widely applied. This is likely to include actions to maintain, for as long as possible, the key features for which the original designation was made, for example by adjusting boundaries. Past experience indicates that intervention strategies tend to be species-specific, and to be strongly advocated, but this must not detract from the more scientific goal of conserving the Arctic’s biodiversity in a holistic manner.

Conserving the Arctic’s changing biodiversity(10.4.8)

Preceding sections have addressed issues such as the effects of climate change on the size and spatial extent of species populations and the communities in which the species occur, the need to conserve genetic diversity, potential problems resulting from the arrival of non-native species, and problems faced by migrant species. This section addresses a few topics that cut across those already discussed. The two main topics discussed here are taxonomy and monitoring.

Biodiversity depends upon taxonomy. It is necessary to be able to name species and habitats, or to understand variation in DNA, to be able to start to think about biodiversity and its conservation, and to communicate thoughts. Taxonomy is therefore fundamental to the work on biodiversity[90]. It is necessary to know the species being considered – knowledge of birds, mammals, and fish is certainly satisfactory, but is this true for all the insects in the Arctic and their roles in the arctic freshwater and terrestrial ecosystems? Knowledge of vascular plants (flowering plants and ferns) is probably satisfactory, but is this true for the mosses, liverworts, lichens, and algae that are responsible for much ofthe photosynthesis, in the sea, freshwaters, and on land? As in almost all parts of the world, is there knowledge about the species of protozoa or bacteria that are associated with the processes of decomposition in arctic soils and in the sediments under lakes or on the sea floor? There are many areas of arctic taxonomy that require exploration and research, and it is vital to the conservation of the Arctic’s biodiversity that these taxonomic subjects are addressed.

Monitoring is important for understanding how the Arctic’s biodiversity is changing and whether actions to conserve this are being successful. As Cairns[91] pointed out, monitoring needs to occur at both the system level and the species level. Monitoring will help now, and in the future, to determine if current predictions are correct and to modify and improve the systems of management. From a scientific perspective, monitoring will allow more data to be collected and, if coupled with research, will also allow a greater understanding of the mechanisms involved with change. In time, therefore, with increasing data and increasing understanding, the conservation of biodiversity would move in the plane shown in Figure 10. 12 from the bottom left hand corner and, perhaps only slightly, toward the top right hand corner. With data and understanding it should be possible in the future to build better models and hence make better predictions.

Conservation of the Arctic’s biodiversity at present relies upon two approaches. One is through the establishment of protected areas, and this was discussed in section 10. 4. 7. Greater knowledge of taxonomy and monitoring of what is happening within those protected areas are both important for their future management. The other approach is more educational, bringing biodiversity thinking into all aspects of life in the Arctic. Considerations of biodiversity need to be explicit in planning for developments at sea or on land. Biodiversity needs to be considered explicitly in the management of land, freshwater, and the sea. Links between biodiversity and the health of the local people need to be established. Biodiversity forms the basis of most tourism into the Arctic, but facilities for tourists need particular care so as not to damage the very reason for their existence[92]. Biodiversity conservation as a concept therefore needs to permeate all aspects of life in the Arctic.

If it is accepted that protected areas are only ever going to cover a relatively small percentage of the land and sea area of the Arctic (possibly between 10 and 20%), then it is the land and sea outside the protected areas that will hold the majority of the Arctic’s biodiversity. Just as within protected areas it is vital to have knowledge of taxonomy and programs of monitoring, there must also be taxonomic knowledge and monitoring throughout the Arctic. The majority of the biodiversity resource in the non-protected areas must not be sacrificed because a minority of that resource is within protected areas. Apart from the Antarctic, it is probably easier to achieve this balance between protected areas and the rest of the land and sea area in the Arctic than in other areas of the world, but it will require international effort if the Arctic’s biodiversity is to be conserved for future generations to use and enjoy. All this, in the face of climate change, will need "building resilience" (the expression used by Rosentrater and Ogden[93]) into all arctic ecosystems, whether or not they lie within protected areas.

 

Chapter 10: Principles of Conserving the Arctic’s Biodiversity
10.1 Introduction
10.2 Conservation of arctic ecosystems and species
    10.2.1 Marine environments
    10.2.2 Arctic freshwater environments
    10.2.3 Environments north of the treeline
    10.2.4 Arctic boreal forest environments    
    10.2.5 Human-modified habitats
    10.2.6 Conservation of arctic species
    10.2.7 Incorporating traditional knowledge
    10.2.8 Implications for biodiversity conservation
10.3 Human impacts on the biodiversity of the Arctic
10.4 Effects of climate change on the biodiversity of the Arctic
10.5 Managing biodiversity conservation in a changing environment

 

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Committee, I. (2012). Effects of climate change on the biodiversity of the Arctic. Retrieved from http://www.eoearth.org/view/article/152370

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