Efforts to sustain ecosystem processes and stem the loss of biodiversity also connect the life Chapter 55 Conservation Biology and Restoration Ecology Overview The Biodiversity Crisis Conservation biology integrates ecology including behavioral ecology evolutionary biology physiology molecular biology and genetics to conserve biological diversity at all levels science with the social sciences economics and humanities Restoration ecology applies ecological principles in an effort to return degraded ecosystems to conditions as similar as possible to their natural predegraded state Some biologists think that about 10 million more species currently exist Others estimate the number to be as high as 200 million Throughout the biosphere human activities are altering trophic structures energy flow Scientists have described and formally named about 1 8 million species of organisms chemical cycling and natural disturbance the accessible surface fresh water The amount of human altered land surface is approaching 50 and we use more than half of In the oceans we have depleted fish stocks by overfishing Some of the most productive aquatic areas such as coral reefs and estuaries are severely stressed Globally the rate of species loss may be as much as 1 000 times higher than at any time in the past 100 000 years Concept 55 1 Human activities threaten Earth s biodiversity Extinction is a natural phenomenon that has been occurring since life evolved on Earth The current rate of extinction is what underlies the biodiversity crisis Humans are threatening Earth s biodiversity The Three Levels of Biodiversity Biodiversity or biological diversity has three main components genetic diversity species diversity and ecosystem diversity All three are being decrease by human activity Genetic Diversity Genetic diversity comprises the individual genetic variation within a population but also the genetic variation among populations that is often associated with adaptations to local conditions If a local population becomes extinct then the entire population of that species has lost some genetic diversity The loss of this diversity is detrimental to the overall adaptive prospects of the species The loss of wild populations of plants also means the loss of genetic resources that could potentially be used to improve crop qualities such as disease resistance Species Diversity Species diversity or species richness is the variety of species in an ecosystem or throughout the entire biosphere The U S Endangered Species Act ESA defines an endangered species as one in danger of extinction throughout all or a significant portion of its range Much of the discussion of the biodiversity crisis centers on species A threatened species are those that are considered likely to become endangered in the foreseeable future Here are a few examples of why conservation biologists are concerned about species loss The International Union for Conservation of Natural Resources IUCN reports that 12 of the 9 946 known bird species and 24 of the 4 763 known mammal species are threatened with extinction The Center for Plant Conservation estimates that 200 of the 20 000 known plant species in the United States have become extinct since records have been kept and another 730 are endangered or threatened About 20 of the known freshwater species of fish in the world have become extinct or are seriously threatened 1 One of the largest rapid extinctions is the ongoing loss of freshwater fishes in East Africa s Lake Victoria About 200 of the more than 500 species of cichlids in the lake have been lost mainly as a result of the introduction of the Nile perch in the 1960s Since 1900 123 freshwater vertebrate and invertebrate species have become extinct in North America and hundreds more are threatened Harvard biologist Edward O Wilson has compiled the Hundred Heartbeats Club a list of species that number fewer than one hundred and are only that many heartbeats away from extinction Several researchers estimate that at the current rate of destruction more than half of all plant and animal species will be gone by the end of this new century Extinction of species may be local when a species is lost in one area but survives in an adjacent one Global extinction means that a species is lost from all its locales We do not know enough about many species to assess their situation The variety of the biosphere s ecosystems is the third level of biological diversity The local extinction of one species especially a keystone predator can affect an entire Ecosystem Diversity community the whole biosphere Each ecosystem has characteristic patterns of energy flow and chemical cycling that can affect For example the productive pastures of phytoplankton in the oceans may help moderate the greenhouse effect by consuming massive quantities of CO2 for photosynthesis and for building bicarbonate shells Some ecosystems are being erased from the Earth at an astonishing pace For example within the contiguous United States wetland and riparian ecosystems have been altered drastically in the past few centuries More than 50 of wetlands have been drained and converted to other ecosystems primarily agricultural Biodiversity and Human Welfare Why should we care about biodiversity Perhaps the purest reason is what E O Wilson calls biophilia our sense of connection to nature The belief that other species are entitled to life is a pervasive theme of many religions and the basis of a moral argument for the preservation of biodiversity Future human generations may be deprived of Earth s species richness Biodiversity is a crucial natural resource Species that are threatened could provide crops fibers and medicines for human use In the United States 25 of all prescriptions dispensed from pharmacies contain substances originally derived from plants The loss of species also means the loss of genes Each species has certain unique genes and biodiversity represents the sum of all the genomes of all organisms on Earth Such enormous genetic diversity has the potential for great human benefit The polymerase chain reaction is based on an enzyme extracted from thermophilic prokaryotes from hot springs Because millions of species may become extinct before we even know about them we will lose the valuable genetic potential held in their unique libraries of genes Humans evolved in Earth s ecosystems and we are finely adjusted to these systems Ecosystem Services Ecosystem services encompass all the