Map of remaining significant woodlands in Southern Ontario. Used to be all woodlands before settlers arrived. Map shows the distribution of converted natural areas in Southern Ontario to human uses (orange). In a 60 year period from 1861 to 1921 the forest cover of Carolinian Canada dropped from 77% to 19 %. In the same time frame, 70% of southern Ontario wetlands were lost. Since that point in time, there has been a slight recovery of forests in some parts of the area but overall the decline and degradation in natural habitats continue. Map shows the extent and distribution of parks and protected areas in Southern Ontario. The Process of Habitat Fragmentation (arrows show increasing fragmentation of habitat) Each new construction results in smaller, more scattered habitats. The outcome is population reduction and isolation for native species. Urban sprawl produces fragmentation and a loss of biodiversity on the planet Habitat Destruction, Loss, Degradation At least 83% of the Earths land surface has been transformed by human activities (Sanderson et al. 2002) About 60% of Earths ecosystems are considered degraded or unsustainably used (Millennium Ecosystem Assessment 2005) 98% of U.S. streams and rivers have been fragmented (see next lecture) by dams (Benke 1990) Habitat Destruction, Loss, Degradation Habitat degradation impacts that affect many, but not all species; some of which may be temporary Habitat destruction & loss impacts that affect nearly all species; time scale for recovery is very long How do humans destroy and degrade habitats and ecosystems? E.g., agricultural activities, extraction activities, certain kinds of development These are often considered to be the most important direct threats to biodiversity, since they eliminate species, reduce population sizes, and reduce performance of individuals Image of shrinking forest cover on Borneo fromHabitat Destruction, Loss, Degradation Loss of forest habitat in Borneo E.g., Hawaiis native bird species Half of the remaining species went extinct soon after Captain James Cook arrived Half went extinct soon after the Polynesians arrived Image of extinct Hawaii (Moho nobilis) from Wikipedia Rare species are especially vulnerable Small populations are especially prone to extinction Images fromMinimum sea ice concentration; 9% decline per decade Habitat Destruction, Loss, Degradation Loss of ice from polar ice cap Map fromBiodiversity Hotspots Usually defined by species richness, endemism & threats Figure from Myers et al. (2000, Nature) Biodiversity Hotspots Usually defined by species richness, endemism & threats These hotspots of biodiversity cover only ~1.5% of the Earths land; if they were destroyed ~1/3 of Earths species would go extinct Designing Nature Reserves Biodiversity can best be sustained by large reserves connected across the landscape and buffered from areas of intense human use. The Best Spatial Configurations for a Core Natural Area or Nature Reserves Larger blocks support larger and more stable populations and communities. 1 large area is better than an equal area composed of many smaller areas because there is less outside influence. The closer ecosystem fragments are to each other, the greater the chance populations will be able to use the entire area. Interconnected areas provide wildlife corridors and permit migration between larger blocks. Buffer zones protect fragmented ecosystems from outside influences. Extensive annual surveys began in the Ontario core areas in 1992 to monitor the Loggerhead Shrike population. During these surveys information on the number of pairs and single birds and their habitats is collected with the help of volunteers. As shown above, the number of shrikes in the province decreased substantially between 1992 (55 pairs) and 1997 (17 pairs). In 1998 the population rebounded slightly to 30 pairs, which is similar to numbers counted in 1995 and The Ontario population is currently at extreme risk of extirpation.