Part 3: Biodiversity

1. Part 3: Biodiversity The Ecosystem Sustainer

2. The BIG Problem • The big problem with invasive species are their impact on biodiversity. • Any kind of pollution inherently reduces biodiversity. • However, invasive species are especially good at this. • Biodiversity is simply the variety of organisms that make up a community. • In other words, are there many species in a community, or only a few? • We want biodiversity to be as high as possible. • The higher the biodiversity, the greater the ability of an ecosystem to withstand disturbances and threats

3. Two Components of Biodiversity • Biodiversity has two components: • 1. Species Richness – the total number of species in a community • 2. Relative Abundance – the number of individuals present for each species • For example, imagine two hypothetical forests • Forest 1 has 25 A’s, 25 B’s, 25 C’s, and 25 D’s • Forest 2 has 80 A’s, 10 B’s, 5 C’s, and 5 D’s • Which one has the greater biodiversity? TPS

4. A B Forest 1 C D Forest 2

5. Biodiversity • Again, we have two forests: • Forest 1 has 25 A’s, 25 B’s, 25 C’s, and 25 D’s • Forest 2 has 80 A’s, 10 B’s, 5 C’s, and 5 D’s • A community with equal relative abundance of each species would have a greater diversity than a second community with the same species richness with a few common species and many rare ones. • In other words, the more even the size of each population, the greater the diversity (all other factors being equal).

6. The three levels • While biodiversity is comprised of two things (species richness, individual abundance), it has three levels: • Genetic Diversity • Species Diversity • Ecosystem Diversity

7. 1. Genetic Diversity • Genetic diversity is simply the genetic variation within a population. • For example, a farm with only one bull has very little variation (every calf has the same sire), whereas a farm with as many bulls as cows has far greater genetic variation. • The greater the genetic diversity, the less prone a species is to extinction. • For example, if there is an epidemic of a disease (e.g CWD), some species may have resistance to it • If all the individuals are similar, they will all be equally susceptible to dying from a disease.

8. 2. Species Diversity • Species diversity is the number of species within an ecosystem • (genetic diversity was the diversity within a species; this is diversity among species). • We want as many species in an ecosystem as possible. • The greater the species diversity, the more capable an ecosystem is of withstanding disturbances and assaults. • For example, the more species there are in a grassland, the more it can resist Queen Anne’s Lace and Canadian Thistle, which displace native grasses and flowers.

9. 3. Ecosystem Diversity • The third measure of biodiversity is the variety of ecosystems on the planet. • Within each ecosystem, roles are performed that sustain global processes • For example, the world’s oceans absorb and trap most of the planet’s CO2 and store it in sugars made by plankton and crustacean shells made of calcium carbonate. • The loss of an ecosystem has devastating ramifications for the natural processes that humans depend on for food, clothing, economics, and our lives as we know them.

10. Invasives and Biodiversity • “The most important characteristic of invasive species is that they not only occur where they are not wanted, but that they do so in numbers large enough to displace desired species and usually they dominate a site to the extent that diversity is greatly reduced.” Cofrin Center for Biodiversity, UWGB • http://www.uwgb.edu/biodiversity/biota/plants/invasiveplants.htm • When an invasive species is able to establish itself in an ecosystem, fewer resources are available to native species. • The introduction of one species lowers both the number of species as well as the abundance of individuals in a species. • This lowers both measures of biodiversity on all three levels. • Increasing invasive species = Decreasing biodiversity