How many species are needed to make an ecosystem work?
Why should we conserve species?
- Theocentric-most religions comment on caring for nature, stewardship, part of creation.
- Biocentric- ethical arguements: living organisms have the right to exist and future generations the right to see organisms we experience now.
- Anthropocentic- Species are fundamental to the ecosystem processes that enrich our lives.
RIO EARTH SUMMIT 1991: BIODIVERSITY
What is the evidence that biodiversity is important for sustaining ecosystem processes?
Natural Capital: Stocks- Flow - Benefit
e.g. Capital stock of soils and trees = Timber, drugs, Clean Water, Aesthetics, Shelter
Environmental degradation changes the stock and reduces the flow.
Bees and pollination
Wildflowers/field/crops- Bee pollination- Apples. citrus, tomatoes, peach, melons, straberries, apricots, cherries, almonds, mangoes, cotton.
Service valued at $112 billion worldwide
Populations are declining dramatically in recent decades- due to pesticide use? disease?
Which species do we need to save?
Models of biodiversity: ecosystem functioning
Model 1- Linear relationship: all species are equally important- if we loose any-direct loss of services.
Model 2- Loss of species has a random effect on a process. Effect on processes is highly dependent on species identity and the order in which they are lost.
Model 3- Many species can be lost before a process is affected-therefore some species are not necessary to fulfilling a process- redundancy.
Which model is most relevant?
The Ecotron (Imperial College 1993/4)
Highly controlled growth chamber- soil, plant, decomposers. herbivores…