The human population is actively modifying Earth’s atmosphere, biosphere, hydrosphere, and lithosphere through resource consumption and the use of technology. Researchers have recognized that the number and magnitude of the environmental problems now facing the Earth are directly correlated to the size of the human population. Humans can influence natural phenomena and processes at the local, regional, and global scale. The various human populations found on our planet also vary greatly in terms of affluence, level of education, and access to health care. The area of knowledge known as sustainable development tries to find solutions to the various social and environmental problems we now face.
Light pollution is the intrusion of unwanted or unneeded artificial light into a man-made or natural environment. A variety of somewhat separate phenomena comprise the...
Population-environment theory and contemporary applicationsLast Updated on 2014-07-24 15:49:49Introduction
Humans have sought to understand the relationship between population dynamics and the environment since the earliest times (1-3), but it was Thomas Malthus’ Essay on the Principle of Population in 1798 that is credited with launching the study of population and resources as a scientific topic of inquiry. Malthus’ famous hypothesis was that population numbers tend to grow exponentially while food production grows linearly, never quite keeping pace with population and thus resulting in natural “checks” (such as famine) to further growth. Although the subject was periodically taken up again in the ensuring decades, it wasn’t until the 1960s that significant research interest was rekindled. In 1963 the U.S. National Academy of Sciences published The Growth of World Population, a report that reflected scientific concern about the consequences of... More »
Predator-prey cyclesLast Updated on 2014-07-08 14:53:04Predator-prey cycles are characterized by regularly spaced increases and decreases in the population sizes or densities of a predator and its prey. Classically, the predator is a carnivorous species and the prey is an herbivorous species. However, carnivores that prey on other carnivores, herbivores feeding on plants, and even parasites attacking their host organisms are sometimes considered to have the same relationship, and so to be predator-prey systems. The predator population’s fluctuations follow those of the prey population through time. That is, the prey population begins to increase while the predator population is still decreasing and the prey population decreases while the predator population is still increasing. The classic (and simplest) explanation of these cycles is that the predator drives the changes in the prey population (by catching and killing its members) and... More »
Metapopulation dynamics of wild dogs in South AfricaLast Updated on 2014-07-02 13:56:37
Ideally, species should be protected in areas large enough to allow for natural demographic and genetic processes. However, in realty, species often occur in small and isolated patches of suitable habitat embedded in human-dominated landscapes. In metapopulation ecology, landscapes are viewed as networks of habitat patches (fragments) in which species occur as discrete local populations connected by migration. The dynamics of such a metapopulation is characterised by (asynchronous) local extinction and recolonisation events.
However, human modification of the landscape between habitat patches, the so-called matrix, often prevents migration. While establishing ‘corridors’ through the matrix may allow dispersing individuals to move from one habitat patch to another, this is often problematic in practice. This raises the question of how metapopulation viability can be... More »
Human population explosionLast Updated on 2014-02-26 17:23:15
Approximately 7.2 billion humans inhabited the Earth in year 2013. By comparison, there might be 500,000 elephants of different kinds, 200,000 chimpanzees, 100,000 gorillas, 20,000 polar bears, 3,000 tigers, 2,000 giant pandas and 200 California condors. Notably, the human population has grown about ten-fold over the past 300 years and nearly four-fold in just the last century. This monumental historical development has profoundly changed the relationship of our species to its natural support systems and has greatly intensified our environmental impact, particularly regarding species extinctions. Equally amazing are the signs that, in our generation, the human population explosion is abating (Figure 1; note that, here and below, many of the values given are estimates and, after the year 2005, projections). Our numbers are expected to rise by another 50%... More »
Sustainable scaleLast Updated on 2013-09-05 00:37:26
Sustainable scale is one of three defining goals (along with efficient allocation and just distribution) of ecological economics. It “refers to the physical volume of the through put, the flow of matter-energy from the environment as low-entropy raw materials, and back to the environment as high-entropy wastes”. Whereas neoclassical economics considers the ecosystem to be a component of the economy, ecological economics assumes the economy to be a subsystem of a fixed ecosystem. Earth, the global ecosystem, is a closed system of a finite size in which only energy passes through. The economy is an open system of variable size in which matter and energy from the ecosystem enter as resource inputs and exit as waste outputs. As the economy expands within the ecosystem, it uses increasing amounts of inputs and expels increasing amounts of waste outputs, requiring larger... More »
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