Concept 56.1: Human activities threaten Earth’s biodiversity Rates of species extinction are difficult to determine under natural conditions The high rate of species extinction is largely a result of ecosystem degradation by humans Humans are threatening Earth’s biodiversity

Three Levels of Biodiversity Biodiversity has three main components: Genetic diversity Species diversity Ecosystem diversity

Genetic diversity in a vole population Fig. 56-3 Genetic diversity in a vole population Species diversity in a coastal redwood ecosystem Figure 56.3 Three levels of biodiversity Community and ecosystem diversity across the landscape of an entire region

Genetic Diversity Genetic diversity comprises genetic variation within a population and between populations

According to the U.S. Endangered Species Act: Species Diversity Species diversity is the variety of species in an ecosystem or throughout the biosphere According to the U.S. Endangered Species Act: An endangered species is “in danger of becoming extinct throughout all or a significant portion of its range” A threatened species is likely to become endangered in the foreseeable future

Conservation biologists are concerned about species loss because of alarming statistics regarding extinction and biodiversity Globally, 12% of birds, 20% of mammals, and 32% of amphibians are threatened with extinction

(a) Philippine eagle Fig. 56-4a Figure 56.4 A hundred heartbeats from extinction (a) Philippine eagle

(b) Yangtze River dolphin Fig. 56-4b Figure 56.4 A hundred heartbeats from extinction (b) Yangtze River dolphin

(c) Javan rhinoceros Fig. 56-4c Figure 56.4 A hundred heartbeats from extinction (c) Javan rhinoceros

Ecosystem Diversity Human activity is reducing ecosystem diversity, the variety of ecosystems in the biosphere More than 50% of wetlands in the contiguous United States have been drained and converted to other ecosystems

Biodiversity and Human Welfare Human biophilia allows us to recognize the value of biodiversity for its own sake Species diversity brings humans practical benefits

Benefits of Species and Genetic Diversity In the United States, 25% of prescriptions contain substances originally derived from plants For example, the rosy periwinkle contains alkaloids that inhibit cancer growth

Fig. 56-6 Figure 56.6 The rosy periwinkle (Catharanthus roseus), a plant that saves lives

The loss of species also means loss of genes and genetic diversity The enormous genetic diversity of organisms has potential for great human benefit

Some examples of ecosystem services: Ecosystem services encompass all the processes through which natural ecosystems and their species help sustain human life Some examples of ecosystem services: Purification of air and water Detoxification and decomposition of wastes Cycling of nutrients Moderation of weather extremes

Three Threats to Biodiversity Most species loss can be traced to three major threats: Habitat destruction Introduced species Overexploitation

Habitat Loss Human alteration of habitat is the greatest threat to biodiversity throughout the biosphere In almost all cases, habitat fragmentation and destruction lead to loss of biodiversity For example In Wisconsin, prairie occupies <0.1% of its original area About 93% of coral reefs have been damaged by human activities

Fig. 56-7 Figure 56.7 Habitat fragmentation in the foothills of Los Angeles

Introduced Species Introduced species are those that humans move from native locations to new geographic regions Without their native predators, parasites, and pathogens, introduced species may spread rapidly Introduced species that gain a foothold in a new habitat usually disrupt their adopted community

Sometimes humans introduce species by accident, as in case of the brown tree snake arriving in Guam as a cargo ship “stowaway”

Fig. 56-8a Figure 56.8 Two introduced species (a) Brown tree snake

Humans have deliberately introduced some species with good intentions but disastrous effects An example is the introduction of kudzu in the southern United States

Overexploitation Overexploitation is human harvesting of wild plants or animals at rates exceeding the ability of populations of those species to rebound Overexploitation by the fishing industry has greatly reduced populations of some game fish, such as bluefin tuna

Fig. 56-9 Figure 56.9 Overexploitation

DNA analysis can help conservation biologists to identify the source of illegally obtained animal products

Concept 56.4: Restoration ecology attempts to restore degraded ecosystems to a more natural state Given enough time, biological communities can recover from many types of disturbances Restoration ecology seeks to initiate or speed up the recovery of degraded ecosystems A basic assumption of restoration ecology is that most environmental damage is reversible Two key strategies are bioremediation and augmentation of ecosystem processes

(a) In 1991, before restoration Fig. 56-21a Figure 56.21 A gravel and clay mine site in New Jersey before and after restoration (a) In 1991, before restoration

(b) In 2000, near the completion of restoration Fig. 56-21b Figure 56.21 A gravel and clay mine site in New Jersey before and after restoration (b) In 2000, near the completion of restoration

Bioremediation Bioremediation is the use of living organisms to detoxify ecosystems The organisms most often used are prokaryotes, fungi, or plants These organisms can take up, and sometimes metabolize, toxic molecules

(a) Unlined pits filled with wastes containing uranium Fig. 56-22a Figure 56.22 Bioremediation of groundwater contaminated with uranium at Oak Ridge National Laboratory, Tennessee (a) Unlined pits filled with wastes containing uranium

soluble uranium (µM) Concentration of Fig. 56-22b 6 5 4 soluble uranium (µM) Concentration of 3 2 1 Figure 56.22 Bioremediation of groundwater contaminated with uranium at Oak Ridge National Laboratory, Tennessee 50 100 150 200 250 300 350 400 Days after adding ethanol (b) Uranium in groundwater

Biological Augmentation Biological augmentation uses organisms to add essential materials to a degraded ecosystem For example, nitrogen-fixing plants can increase the available nitrogen in soil

Exploring Restoration The newness and complexity of restoration ecology require that ecologists consider alternative solutions and adjust approaches based on experience