Biodiversity – Dr Martin Hodson

We were treated to an excellent talk, “Biodiversity”, given by the environmental biologist, Dr Martin Hodson, a lecturer and researcher at both Oxford Brookes and Oxford Universities. After detailing the history of the study of biodiversity, Martin gave details of the current number of identified species (1.2M) and said that it was believed that 86% of species had not yet been identified. The number and distribution of plants and therefore other living species varied depending on the habitat, with regions enjoying warmer wetter climates, such as tropical rain-forests, supporting the greatest variety of species. 17 countries contain 75% of the world’s biodiversity with hotspots in the Sunda Islands, the Philippines and Madagascar, all areas which are undergoing substantial man-made environmental change.
Extinction rates have increased as the human population has increased with 24% of mammals and 11% of birds threatened with extinction caused by human activities. The rate is 1000 times greater than that observed in fossil records. The reasons for this rate of extinction are:

  • Direct causes – hunting and collection e.g. whales, overfishing etc.
  • Indirect causes – habitat depletion and degradation e.g. buildings, road etc . This is by far the largest cause of extinction
  • Competition with invasive species
  • Pollution
  • Global climate change in the future

It is believed that we are entering the Sixth Mass Extinction Period in the earth’s history. Previous mass extinctions were caused by natural phenomena such as the ice age and comet collisions.

Why conserve biodiversity? There are three main ethical views:

1. Anthropocentric view. There are unknown species, especially plants, that could be useful to humans
2. Ecocentric view. Too many links in the system will be broken causing a collapse of the whole ecosystem
3. Biocentric view. Important to increase the number of species that are particularly desirable.


Environmentalists are viewing the value of biodiversity in terms of the ecosystem services provided.

The most recent idea on valuing biodiversity is TEEB – The Economics of Ecosystems and Biodiversity i.e. placing a monetary value on the environment e.g. maintaining mangroves to protect coastlines from flooding is more economic than clearing them for farming prawns.