Topic 5.2 / Option D.3 Human Impact on Ecosystems 1 Measuring and Preserving Biodiversity Assessment Statements: 5.2.4, G.3.1 – G.3.3

Measuring biodiversity Biodiversity takes two factors into account: –Species richness, which is the number of species –Species evenness, which is how evenly the total number of individuals are spread among the different species. Two ecosystems could have 5 species each and 1000 total individuals, yet one could have even numbers of each species and another could be nearly a monoculture. The one that is more even has more biodiversity. Remember that stable communities do not have even populations of different species due to the shape of the trophic pyramid. It may make more sense to look at diversity of each trophic level separately

Calculating biodiversity: The Simpson Index D = N(N-1) Σ(n(n-1)) Where: D = biodiversity N = total number of all organisms of all species n = number of individuals of a specific species When D is high, there is a lot of biodiversity, such as in a stable community that is in an advanced successional stage. When D is low, there is limited biodiversity, such as in a community that has recently experienced a disturbance or where an invasive species is taking over.

The importance of biodiversity: ethical reasons Humans feel connected to nature and other forms of life for its beauty and the sense of peace it gives. We believe that other species are entitled to life and we need to preserve and protect them. It is our moral obligation to preserve biodiversity for future generations. Stewardship for the earth and its inhabitants is a main tenet of many religions.

The importance of biodiversity: ecological reasons Ecosystems and their inhabitants provide a number of services that help make all life possible, including: –Purification of air and water –Reduction of severity of droughts, floods and other weather extremes –Generation and preservation of fertile soil –Detoxification and decomposition of wastes –Pollination and dispersal of vegetation –Nutrient cycling –Protection against erosion –Protection against UV radiation

The importance of biodiversity: economic reasons Many species provide economic benefits to humans, including: –Present and future food crop species –Present and future building materials or fuel sources –Present and future medicines –Present and future natural fibers –Present and future genes for use in genetic technology Ecosystems also provide economic benefits through ecotourism and recreation.

The importance of biodiversity: aesthetic reasons Humans tend to believe that nature is beautiful and we want to preserve that beauty. A pristine forest is better looking than a strip mine. Nature calms us and provides subject matter for our artists, including painters, writers, composers etc.

The precautionary principle What usually happens: People concerned about an environmental issue have to prove that it is a problem before it will be fixed. The precautionary principle: People who want to cause a change to the environment must prove that it will do no harm before proceeding “An ounce of prevention is worth a pound of cure” “To keep every cog and wheel is the first precaution to intelligent tinkering.” - Ecologist Aldo Leopold