Environmental Biology
Essay Question 1 Explain how changes in habitat can lead to habitat fragmentation. How does this affect the population of animals in that area? Species lose their habitats when those habitats are destroyed outright, but habitat loss also occurs when habitats are altered through more subtle processes, including fragmentation and other forms of degradation. The sudden and complete elimination of habitat is uncommon at large scales; instead, what we usually witness is gradual, piecemeal degradation, such as habitat fragmentation. Nearly every human activity can alter or destroy habitat.
Farming replaces diverse natural communities with simplified ones of only a few plants species (certain crops). Grazing modifies the structure and species composition of grasslands. Either type of agriculture can lead to desertification. Clearing forests removes the food, shelter, and other resources that forest dwelling organisms need to survive. Farming, logging, and road building, and other type of human land use and development often intrude into forested habitats, for example, breaking up a continuous expanse of forest into an array of fragments, or patches.
Animals and plants adapted to unbroken forest will die out as a forest becomes fragmented. As habitat fragmentation proceeds across a landscape, species requiring the habitat gradually disappear, fading out from one fragment to another. Essay Question 2 What are the major causes of biodiversity loss (we talked about during lecture)? Why should we be concerned? Overall, scientists have identified four primary causes of population decline and species extinction: habitat loss, invasive species, pollution, and over harvesting.
Global climate change now is becoming the fifth. Each of these causes is intensified by human population growth and by our increase per capita consumption on resources. We should be concerned since there are many tangible, pragmatic ways that biodiversity benefits people and supports human society. Another is to focus on the ethical dimensions to biodiversity preservation, because many people feel that organism have an intrinsic right to exist. Some things in life can indeed be free—as long as we protect the ecological systems that provide them.
Intact forests provide clean air and water, and they buffer hydrologic systems against flooding and drought. Native crop varieties provide insurance against disease and drought. Abundant wildlife can attract tourists and boost the economies of developing nations. Intact ecosystems provide these and other valuable processes, known as ecosystem services, for all of us, free of charge. Biodiversity helps maintain ecosystem function, enhances food security by providing the food we eat, provides drugs and medicines, and generates economic benefits through tourism and recreation.
