Download Habitat Fragmentation - Introduction to Conservation Biology - Lecture Notes and more Study notes Biology in PDF only on Docsity! Conservation for All Chapter 5 Habitat Fragmentation Breaking apart of continuous habitat. Three effects: less vegetation, continuous habitat becomes remnants or patches and new forms of land-use replace lost vegetation. Author proposes that habitat fragmentation isn’t as useful a term as is “land-use change.” This chapter discuss patterns and processes around land-use change. Theory of Island Biogeography. Reminder of this – predicts that large islands close to a mainland will have the greatest number of species. Islands became patches. This was later replaced by a patches and corridors within a matrix because patches of habitat aren’t exactly like islands and the state of the matrix matters. The degree of isolation depends on use of the matrix. Some scientists broke this down into categories: (1) intact (2) variegated (3) landscapes where the fragments are a minor part of the landscape (fragmented) and (4) relict – little remaining habitat. Suggests thinking about habitat as a mosaic rather than “habitat and non habitat.” Why have a “landscape” rather than a “fragment” perspective? (i) landscapes have properties that differ from those of fragments (Figure 5.1); (ii) many species move between and use multiple patches in the landscape; and (iii) conservation managers must manage entire landscapes (not just individual fragments) and therefore require an understanding of the desirable properties of whole landscapes. Landscape change isn’t random. Where is it most likely to occur? Flat spots. Places left are too steep, floodplains or poor soils. Edge effects. Biophysical changes. Box – Extinction debt and time lag. Can’t assume that species in fragments will persist there over time. This is one reason why long-term studies are important. Fig,. 5.4. Fewer organisms persist in smaller fragments. Might be due to breeding or foraging needs Different species respond in different ways to landscape change. Population size is influenced by birth, death, immigration, and emigration. These processes are also influenced by some processes. Deterministic processes: hunting, pesticides, insecticides or other chemicals; hunting by humans; harvesting and removal of plants; and construction of roads with ensuing road kills of animals. Isolation. Depends on the species and the matrix of habitat. This can be reduced by corridors or “stepping stones” Author suggests coffee plantations may be a corridor!!! YAY!! Stochastic processes: Talked about this on Friday. Chance events. Chance changes in the demography. Loss of genetic variation, which may happen with inbreeding, genetic drift, or founder effect (could be offset by a rescue effect). Docsity.com
