Evaluating Biodiversity and Vulnerability

Identifying factors that lead to loss of diversity

Main five pressures on biodiversity are still present and even intensifying:

1. Habitat loss and degradation
2. Climate change
3. Excessive nutrients and other pollutants
4. Over-exploitation and unsustainable use of resources
5. Invasive alien species

There is something known as the Red List that shows the status of species in terms of their conservation status. You can see the list here.

It should be mentioned that biodiversity conservation is crucial. Biodiversity, be it genetic, habitat, or species, is one of the determining factors in an ecosystem's health. The above mentioned factors are putting pressures on the planet that it cannot absorb fast enough. Ecological footprints are exceeding the Earth's capacity to recover. All of this leads to a persistent loss in biodiversity that slowly reduces our ecosystems' resilience and compromises the resources on which we depend.

There are certain world trends that are occurring around the world:
- Habitats are declining.
- Abundance and distribution of species are declining.
- Change in status of threatened species.
- Threats in genetic diversity in domestic animals, cultivated plants, and fish species. This is due to interference with natural selection.
- Coverage of protected areas are increasing
- Marine Trophic Index has shown an increase, but has regional fluctuations.
- Ecosystems have become more fragmented.
- Water quality in aquatic ecosystems has been declining. Some areas have increased their water quality by dealing with point-source pollution.
- Nitrogen deposition has increased.
- The amount of invasive species has increased and are now a threat.
- Areas of forest, agricultural, and aquaculture ecosystems under sustainable management have increased, but there are several areas that still require more efforts.
- Humanity's Ecological Footprint is still rising.

Measuring Biodiversity

Biodiversity is the total amount of different species that are found in a given ecosystem, biome or the entire planet. It is an indicator of the health of an area. The greater biodiversity there is, the healthier the ecosystem is.

There are several ways to measure the biodiversity of a given area. The two most popular indices are the Shannon Index and the Simpson Index.

However, before we can talk about measuring biodiversity, two key terms we should know are richness and evenness.

Richness: Number of species per sample.

Evenness: Relative abundance of the different species making up the richness of the area.

The Shannon Index

H= Shannon Diversity Index

S= Total # of species in a community (richness)

Pi= Proportion of S made up of ith species

Eh= Equitability (evenness)

Equitability is measured H/Hmax. Hmax=lnS

To learn more about the Shannon Index go here: http://www.tiem.utk.edu/~mbeals/shannonDI.html

The Simpson's Index

It measures the probability that two individuals randomly selected belong to the same species (or other category)

n= total # of organisms of a particular species (in plants, the % of coverage is measured)

N= total # of organisms of all species

There is also Simpson's Index of Diversity, which measures the probability that 2 randomly selected individuals in a zone belong to different subspecies.

The formula is 1-D.

Finally there is the Simpson's Reciprocal Index, which measures the number of equally common subspecies that will produce the observed Simpson's index.

The formula is 1/D

For more information: http://www.countrysideinfo.co.uk/simpsons.htm