Chapter 16. Chapter 16: Conversation and Biodiversity

The observed drop in oxygen level correlated with the proliferation of bacteria that were using up methane. This confirmed scientists’ suspicion that bacteria were the cause of the disappearance of methane. Scientists also discovered, through DNA testing, that the bacteria responsible for consuming oil were also found at other oil spills. These bacteria live in the Gulf at all times, because there are naturally occurring oil leaks in this area.

Biodiversity can be defined as the diversity of species in an area, the diversity of genes and alleles for a particular species, and the number of different ecosystems in an area.

Studying biodiversity can be difficult because more than just the number of species must be studied—including the diversity of genes and alleles and the diversity of ecosystems.

Three primary factors contribute to species richness. (a) The solar energy available: More available solar energy correlates with greater species diversity. The sun’s solar energy is more concentrated in areas closer to the equator and less concentrated in areas farther away from the equator. The more energy available, the greater the number of organisms and species that can be supported. (b) The evolutionary history of the area: The greater the time that has elapsed in an undisturbed inhabited area, the greater the biodiversity. Climatic disasters in an area diminish the number of species and lower biodiversity. (c) The rate of environmental disturbance: Environments with an intermediate amount of disturbance have the greatest biodiversity. Species that would outcompete (have a competitive advantage over) many other species may be lost from the environment due to disturbance, enabling greater species diversity.

The fewer the individuals making up a species, the greater the chances of the species becoming extinct. As the population of tigers has decreased, their genetic/allele diversity has decreased. Should tigers be faced with a severe environmental disturbance, disease, or other change, the population may lack the alleles that would permit some individuals to survive and reproduce.

The chief reason for species loss is habitat loss and habitat degradation due to human activities, particularly in tropical rain forests. It is estimated that half the world’s tropical rain forests have been destroyed over the past 25 years. These areas are biologically very diverse, and their loss represents a significant loss in biodiversity. Overexploitation of species and the introduction of exotic species are additional reasons for the loss of so many species.

Once a species is lost, it can never exist again. Each species has formed as the result of a unique, uninterrupted, never to be repeated evolutionary history that gave rise to a genome unlike any other.

Exotic species may: (a) become invasive, since they often have no natural predators, leading to uncontrolled population growth, and (b) find prey that have no natural defenses against them, causing endangerment or extinction of these specie. Communities or whole ecosystems can be altered as a result of invasive species. This can cause degradation of the environment and species loss.

Fossil fuels, which include oil, coal, and natural gas, are composed primarily of carbon and hydrogen, with smaller amounts of nitrogen and sulfur. As fossil fuels are burned, these elements react with oxygen in the air to form carbon dioxide, water, nitrogen dioxide, and sulfur dioxide.

Carbon dioxide and methane in the air absorb infrared energy radiating from the earth, preventing its escape into space and thus heating up the atmosphere. With carbon dioxide and methane added to the atmosphere, more heat is retained and contributes to global rises in temperature. This effect is comparable to that of the glass panes of a greenhouse, which have the same effect as carbon dioxide and methane in retaining more infrared energy and warming the internal environment of the greenhouse.

(a) Reducing biodiversity: A disproportionate percentage of the world’s species live in the rain forests. With the disappearance of these forests, many known and unknown species are lost. (b) Reducing photosynthesis and increasing greenhouse gases: Each year, an estimated 610 billion tons (550 trillion kg) of carbon dioxide, a greenhouse gas, are removed from the atmosphere during photosynthesis by the plants found in tropical rain forests—an amount that will be reduced as rain forests are destroyed. Additionally, when rain forests are burned, carbon dioxide is released, adding more greenhouse gas to the atmosphere.

As a result of the reduced production and use of CFCs, atmospheric ozone levels have stabilized and a full recovery is thought possible. Images of the ozone hole over the Antarctic revealed that it was increasing in size until 2010, when it was found to have stopped enlarging as atmospheric levels of ozone stabilized.

The primary impact of the difficulty in defining biodiversity is identifying which organisms to include in conservation goals, given that conservation resources are limited. Identifying which species are to be protected can be very challenging, and this is made more difficult by the fact that many species and their value have yet to be identified.

A keystone species, such as kelp, has a disproportionate effect on the biodiversity of a community, as is revealed if that species should die out or otherwise be removed. When a keystone species is lost from a community, a relatively large number of other species, which depend on it, directly or indirectly, are also lost.