CONSERVATION AND BIODIVERSITY 4.2 Evaluating Biodiversity and Vulnerability

Assessment Statements  Identify factors that lead to loss of diversity.  Discuss the perceived vulnerability of tropical rainforests and their relative value in contributing to global biodiversity.  Discuss current estimates of numbers of species and past and present rates of species extinction.  Describe and explain the factors that may make species more or less prone to extinction.  Outline the factors used to determine a species’ Red List conservation status.

Assessment Statements  Describe the case histories of three different species: one that has become extinct, another that is critically endangered, and a third species whose conservation status has been improved by intervention.  Describe the case history of a natural area of biological significance that is threatened by human activities.

4.2.1 Identify factors that lead to loss of diversity.  Factors that lead to loss of diversity include:  Natural hazards (volcanoes, droughts, ice ages, meteor impacts)  Habitat degradation, fragmentation, and loss  Agricultural practices (monoculture, pesticide use, use of genetically modified species)  Introduction of non-native species  Pollution  Hunting, collecting, and harvesting

4.2.2 Discuss the perceived vulnerability of tropical rainforests and their relative value in contributing to global biodiversity.  Tropical rainforests are one of the two most species-rich and biodiverse ecosystems on Earth.  Scientists believe they may contain half of all species on Earth, with many existing only in the canopy, and many not found anywhere else.  They are under constant threat: an average of 1.5 hectares are lost every four second, which is driven by external demands for timber, beef, soya and biofuels.  Valuing them as carbon stores is helping a little.

4.2.2 Discuss the perceived vulnerability of tropical rainforests and their relative value in contributing to global biodiversity.  Rainforests have thin- nutrient poor soils, which means it is difficult for them to re-grow once cleared.  Small disturbances recover fairly quickly, but large ones do not.  Also if only a limited amount of timber is taken it can re-grow quickly, but too much means it will not reach climax community.

4.2.3 Discuss current estimates of numbers of species and past and present rates of species extinction.  Five mass extinctions:  Cretaceous-Tertiary 65 m.y.a. – asteroid impact, 16% marine families, 47% marine genera, 18% land vertebrate families  End Triassic 200 m.y.a.– lava erupting, 23% all families, 48% all genera  Permian-Triassic 250 m.y.a. – asteroid/comet impact, 95% all species, 53% marine families, 84% marine genera, 70% all land species

4.2.3 Discuss current estimates of numbers of species and past and present rates of species extinction.  Late-Devonian 364 m.y.a. – unknown cause, 19% all families, 50% all genera.  Ordovician-Silurian 439 m.y.a. – drop then rise in sea level, 27% all families, 57% all genera.  m.y.a. – million years ago  Past extinction occurred suddenly over relatively short period of time, caused by environmental catastrophes.  Animals and plants died from initial event and short-term environmental turmoil that followed.

4.2.3 Discuss current estimates of numbers of species and past and present rates of species extinction.  Total number of species currently on Earth is poorly understood. Current estimates are between 5 and 100 million, but we have only identified 1.8 million so far.  Hard to get an accurate count, because most species not discovered and described are very small: insects, bacteria, and other microbes.  Current mass extinctions are happening at a faster rate, which does not give species time to adapt to changing conditions. 27,000 species per year from rainforests.

4.2.4 Describe and explain the factors that may make species more or less prone to extinction.  Factors that make animals more prone to extinction:  Small population size and limited distribution  Habitat specialists(specific diet or habitat requirements)  Low reproductive capacity  Poor competitors  Large mammals(ready source of meat)  Valuable products  Altruistic species(stick together)  Clumping(requires large numbers for survival)  Position in food chain(Top predators)

4.2.5 Outline the factors used to determine a species’ Red List conservation status.  Factors used to determine conservation status:  Population size  Reduction in population size  Numbers of mature individuals  Geographic range and degree of fragmentation  Quality of habitat  Area of occupancy  Probability of extinction