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Amphibians: Tough Times for Toads and Frogs Last Updated on 2014-10-12 17:09:37 Amphibians have not fared very well in recent years. Since 1980, 32.3% of amphibious species (1,856 out of 5,743 known species) have declined in population size, 7.4% sit on the brink of extinction, and between 0.2% and 2.1% have already disappeared. [1] This contrasts with birds and mammals for which, respectively, 12% and 23% have declined over the same period, 1.8% and 3.8% are near extinction, and 0.05% and 0% have already disappeared. [1] Loss of suitable habitat has been a critical factor in the decline of all four families. In addition, 21 species in the Ranidae family are threatened by overexploitation from excessive harvesting for human consumption, especially in Asia. At first, the decline in populations of 80 species in the Bufonidae, 38 species in the Hylidae, and 47 species in the Leptodactylida seemed puzzling because it was occurring even in areas protected from... More »
Module: Advanced Topics in Remote Sensing Last Updated on 2011-06-07 00:00:00 SUMMARY Data Description Landsat Data has been prepared for each participating campus. Using the 30 yr Landsat period from 1975 to 2005, data can be used to examine changes in land cover, abundance of vegetation in the summer (peak abundance) and relate changes to climate conditions. Each Landsat scene covers an area approximately 185 km x 185 km and the data is provided in a digital format. Landsat data from 1975 to 2005 was acquired for each campus location. Data consisted of an image from 1975, and one each from 1990, 2000 and 2005. Summer images were selected to acquire data near the time of maximum vegetation cover. CAVEAT: data was not acquired on the exact same date each year due to cloud cover or other data problems however, all images were collected within the same very small time frame. Landsat 1975 data was acquired by the Multispectral Scanner (MSS), the... More »
Invasive Plant Abundance Last Updated on 2011-02-01 00:00:00 Home and Away: Are Invasive Plant Species Really That Special? Invasive plants are a major environmental problem--but how abundant are they? Invasive plant species are a serious environmental, economic and social problem worldwide. Their abundance can lead to lost native biodiversity and such ecosystem functions as nutrient cycling.   Despite substantial research, however, little is known about why some species dominate new habitats over native plants that technically should have the advantage. A common but rarely tested assumption, say biologists, is that these plants behave in a special way, making them more abundant when introduced into communities versus native plants that are already there. If true, it would mean that biosecurity screening procedures need to address how species will behave once introduced to nonnative communities--very... More »