AR

Chapter 54: Biodiversity and Conservation Biology

  • The growing field of conservation biology is making progress in studying, preserving, and restoring biodiversity.

54.1 What is Biodiversity?

  • In essence, biodiversity means biological diversity.
  • Genetic diversity is the total genetic information contained within all individuals of a population, species, or group of species.
    • Genome sequencing is a research protocol that sequences the entire genome of multiple members of the same species.
    • Environmentαl sequencing is a research protocol that sequences all or most of the genes and/or alleles present in a sample taken from the soil or water present in a habitat (or your gut).
    • ==Genetic diversity is important because it represents the adaptive capacity of a population or higher taxonomic group一the ability of that group to persist over time.==
  • The diversity of species present is a key feature of biological communities. It is usually qualified in two ways:
    • Species richness is a count of how many species are present in a defined area (which may vary in size from local to regional).
    • Species diversity is a weighted measure that incorporates both species richness and evenness, the relative abundance of each species present.
  • One new technique for identifying species is called DNA barcoding-the use of well-characterized gene sequences to distinguish species.
    • ==The idea is that variation in one gene is higher between species than within species.==
  • Thus, ecologists increasingly turn to newer measures of diversity at the species level:
    • Phylogenetic diversity; In terms of evolution, some species give a community evolutionary distinctiveness because they are phylogenetically distant from other species.
    • Functional diversity; In terms of ecology, some species have functional traits that play a key role in the function of an ecosystem.
  • Ecosystem diversity is a measure of these complex factors plus interactions with the abiotic environment.
  • Intertwined with the concept of ecosystem diversity is ecosystem function, which refers to the sum of biological and chemical processes that are characteristic of a given ecosystem-such as primary production, nitrogen cycling, decomposition, and carbon storage.
  • In 1988, conservation biologist Norman Myers pioneered the term biodiversity hotspot to characterize regions that are in most urgent need of conservation action-areas where efforts to preserve habitat would have the highest return on investment.

54.2 Threats to Biodiversity and Ecosystem Function

  • An endangered species is a species whose numbers have decreased so drastically that it is almost certain to go extinct unless effective conservation programs are put in place.
  • Humans cause habitat destruction, the physical and functional loss of habitats, by many methods:
    • Logging and burning forests
    • Damming rivers
    • Dredging or filling estuaries and wetlands
    • Plowing prairies and grazing livestock
    • Excavating minerals and fuels
    • Building housing developments, golf courses, shopping centers, office complexes, airports, roads, and other structures
  • Aside from destroying natural areas outright, human activities can also cause habitat degradation, a reduction in the quality of a habitat. Humans can degrade habitats in many ways, for example:
    • Artificial lights disorient migrants and disrupt night foraging.
    • Traffic noise interrupts communication and causes stress.
    • Pet cats have contributed to at least 63 vertebrate extinctions.
  • One of the most pervasive patterns of habitat degradation is habitat fragmentation-dividing contiguous areas of natural habitats into small, isolated fragments.
  • Overexploitation refers to any unsustainable removal of organisms from the natural environment for use by humans.
    • ==Overexploitation is especially important in marine environments.==
  • A nonnative species that are introduced into a new area is called an exotic species.
    • Exotic species do not necessarily pose problems, and they can even be beneficial in some circumstances.
    • But some exotic species directly threaten native species by eating them, competing with them, causing disease, or other types of deleterious interactions.
  • If an exotic species is introduced to a new area, grows to large population size, and disrupts species native to the area, it is called an invasive species.
  • Given reasonable projections of how much habitat will be lost over a given time period, biologists can estimate rates of extinction based on species-area relationships.
    • ==The concept here is to track backward on a species-area curve.==

54.3 Why Are Biodiversity and Ecosystem Function Important?

  • Resistance is a measure of the extent to which a community remains unchanged during a disturbance.
  • Resilience is a measure of how quickly a community recovers following a disturbance.
  • A natural experiment occurs when comparison groups are created by an unplanned, unmanipulated change in conditions.
  • Considered collectively, all the direct and indirect benefits that humans derive from organisms and the ecosystems they compose are called ecosystem services.
  • Bioprospecting is the exploration of bacteria, archaea, protists, plants, fungi, and animals as novel sources of drugs or ingredients in consumer products-has benefited from the recent explosion of genetic information.

54.4 Preserving Biodiversity and Ecosystem Function

  • The way forward involves both reducing population growth and improving sustainability-the managed use of resources at a rate only as high as the rate at which they are replaced.
  • Agricultural scientists are racing to preserve diverse strains of crop and wild plants in seed banks-long-term storage facilities to avoid the loss of genetic diversity in local and global populations.
  • Some species-including Pere David’s deer and the northern white rhinoceros are extinct in the wild and exist only in captivity.
    • These animals are examples of ex situ conservation, the preservation of species in zoos, aquaria, or other artificial settings.
  • One long-term solution to enabling gene flow among isolated populations is the establishment of wildlife corridors, strips of undeveloped habitat that connect preserved areas.