If biodiversity is so precious and important, then why is it so threatened?

1. If biodiversity is so precious and important, then why is it so threatened? • Distinguish between physical agents of biodiversity loss, and the underlying policy and social reasons • Existence of trade-offs- those actions harmful to one component of nature also provide valuable societal benefits (Tilman 1999) • Much of current environmental policy is rooted in policy developed for an older and much different world Dr. John A. Finn University of Reading

2. Social, cultural and economic driving forces that cause reduced biodiversity need addressing: a) difference between value to individual and society need to be removed, especially where irreversible damage caused b) reform social and economic policies that drive species loss c) more research and institutions for biodiversity conservation. Science has an integral role in contributing to policy reform; “Society invests in science because science benefits society” Folke et al, 1996 Dr. John A. Finn University of Reading

3. Human population in the biodiversity hotspots. • 25 biodiversity hotspots that have exceptionally high species richness and endemicity. Are also very threatened by human activities. (Cincotta et al. Nature 404: 990-992.) • Overhead- indicates relationship between biodiversity hotspots and population pressure Dr. John A. Finn University of Reading

4. “The world that exists in 100 and 1000 years will be of human design, whether deliberate or haphazard. Principles of design need to be based on science and ethics” Tilman 1999 Dr. John A. Finn University of Reading

5. References for previous section: • Biological diversity, ecosystems and the human scale. 1996. Folke et al. Ecological Applications 6: 1018- 1024. (electronically available through library) • Causes, consequences and ethics of biodiversity. 1999 Tilman, D. Nature 405: 208-211. (electronically available through registration at Nature website http://www.nature.com/nature/info/insights.html) • Human population in the biodiversity hotspots. Cincotta et al. Nature 404: 990-992. Dr. John A. Finn University of Reading

6. Biodiversity and ecosystem function: pattern, process and prospects Dr. John A. Finn Department of Agriculture, The University of Reading

7. Experimental reductions in biodiversity "On average, plants contain less than half a gram of carbon per square metre. Yet this thin veneer of living matter sandwiched between a 100km deep lithosphere and a 100-km high atmosphere manages to cycle about 60 gigatonnes (60 x 1015) of carbon per year between the biosphere, lithosphere and atmosphere. Clearly the Earth's biota has staggering capability to affect our environment.” But this perspective overlooks a critical feature of plant life: this green slime consists of more than a quarter of a million species. What, if any, is the role of such extraordinary diversity? ” Naeem [1999] Dr. John A. Finn University of Reading

8. low high Hypothetical relationships between diversity and ecological processes Redundant Rivet Idiosyncratic Ecosystem function low high low high Species richness Dr. John A. Finn University of Reading

9. Ecosystem function low high Species richness Relationship between diversity and function • Null hypothesis: ecosystem function is insensitive to species additions or deletions (the trivial case) Dr. John A. Finn University of Reading

10. Ecosystem function low high Species richness What are ecosystem effects of a reduction in diversity? • Rivet: all species contribute to the integrity of an ecosystem in a small but significant way such that a progressive loss of species steadily damages ecosystem function. Dr. John A. Finn University of Reading

11. Ecosystem function low high Species richness Relationship between diversity and function • Redundant:the contribution of additional species is redundant above a critical level Dr. John A. Finn University of Reading

12. Ecosystem function low high Species richness Relationship between diversity and function • Idiosyncratic hypothesis: ecosystem function changes unpredictably as species richness changes Dr. John A. Finn University of Reading

13. BIODiversity and Ecosystem Processes in Terrestrial Herbaceous systems: an EU funded project examining the importance of biodiversity for ecosystem functioning. • Diversity gradient of: • species richness (five levels) • functional group richness (three levels) Simulated loss of plant species from background level to single species • Eight European sites, 2m X 2m plots, ~60 plots each site • measured: above-ground biomass, soil nutrients, insect herbivory, weed invasion etc. Dr. John A. Finn University of Reading

14. Novel contribution of BIODEPTH: • Experimentally varies diversity at a local scale: diversity is a determinant variable • Varies composition within each diversity level • Independently varies species richness and functional group richness • Measures a variety of ecosystem processes, not just yield • Designed to permit analyses that identify contribution of sampling effect and complementarity, i.e. the mechanisms by which diversity exerts and influence • Replicated experiment conducted at several sites across a large spatial scale Dr. John A. Finn University of Reading

15. Decreasing species richness (log2 scale) Dr. John A. Finn University of Reading

16. The previous slide show the relationship between diversity and aboveground biomass at each of the local sites (countries). When each data set from individual sites were analysed individually, the relationship was best described by a variety of models: linear (Portugal and Switzerland); curvilinear ( Germany, Sweden, Sheffield); ANOVA (Ireland and Silwood). Dr. John A. Finn University of Reading

17. Dr. John A. Finn University of Reading

18. The previous slide shows a ‘meta-analysis’ (combined analysis) of all of the data simultaneously. The analyses attributed variation mostly to location (30% of variation), diversity (20%) and species composition (40%). There was no significant diversity*location interaction. This means that the shape of the relationship between biomass and diversity at each site did not differ significantly. Thus, overall, the relationship was described as a log-linear reduction in biomass as diversity decreased. This corresponds to a general reduction of about 80 g biomass per sq. metre for each halving of species richness in European grasslands. Dr. John A. Finn University of Reading

19. Explanations for differences between single sites and meta-analysis • (i) all sites conform to the same underlying pattern seen in the overall analysis, and differences between individual sites are due to reduced sample size and statistical power • (ii) sites do differ in their responses, but the overall analysis is not powerful enough to reveal a significant location-by-species richness relationship • (iii) a significant general pattern emerges despite differences in detail at individual locations; while at any single location the effect of changes in species richness may vary from strong (e.g. Portugal, Switzerland) to undetectable (e.g. Greece), but on average we would expect productivity to decline as species richness declines. Dr. John A. Finn University of Reading

20. Dr. John A. Finn University of Reading

21. Processes to explain relationships between diversity and ecosystem function • ‘Sampling effect’ or ‘selection probability effect’ • Niche complementarity • Positive species interactions e.g. mutualisms Dr. John A. Finn University of Reading

22. Processes (contd)The Sampling Effect • The sampling effect: • more diverse communities have a greater probability of containing and becoming dominated by, a highly productive species. • Important biological property of ecological systems OR • artefact of species richness experiments and random assemblages, a ‘hidden treatment’ Dr. John A. Finn University of Reading

23. How might biodiversity relate to ecosystem function? • 2. Niche complementarity- ecological differences between species lead to more complete utilisation of available resources in more diverse communities. • Granivorous ants/rodents feeding on different sized seeds; microhabitat preferences in animals • Different rooting depths by plants, different degrees of shade-tolerance etc. • 3. Mutualisms- A reduction in positive mutualistic interactions among species in more depauparate and simplified communities. Dr. John A. Finn University of Reading

24. Niche complementarity: Within- and between- FG diversity FG 1 SP 1 SP 2 FG 2 SP 3 SP 4 FG 3 Ecological differences between species lead to more complete utilisation of available resources in more diverse communities. Differences between species of different functional groups are expected to be greater than differences between species of the same FG Dr. John A. Finn University of Reading

25. Dr. John A. Finn University of Reading

26. The insurance hypothesis: More diverse assemblages will have a greater probability of having species that are adapted to changed conditions Stable conditions 7 spp 1 spp 6 spp 1 spp Environmental fluctuation Contribution of each species to ecosystem function Species richness Dr. John A. Finn University of Reading

27. The Insurance Hypothesis:more diverse assemblages have a greater probability of containing species that are adapted to changed conditions 10 sp. process rate 1 sp. 2 sp. 4 sp. constant conditions variable conditions Dr. John A. Finn University of Reading

28. The Insurance Hypothesis:more diverse assemblages have a greater probability of containing species that are adapted to changed conditions 10 sp. ecological process 4 sp. 2 sp. 1 sp. constant conditions variable conditions Dr. John A. Finn University of Reading

29. Further references on function-diversity work: • Hector, A. et al. (1999) Plant diversity and productivity experiments in European grasslands. Science,286, 1123-1127. (BIODEPTH project) • Hooper, D.U. (1998) The role of complementarity and competition in ecosystem responses to variation in plant diversity. Ecology,79, 704 - 719. • Jonsson, M. and Malmqvist, B. 2000. Ecosystem process rate increases with animal species richness: evidence from leaf-eating, aquatic insects. - Oikos 89: 519-523. • Tilman, D., Knops, J., Wedin, D., Reich, P., Ritchie, M. & Siemann, E. (1997a) The influence of functional diversity and composition on ecosystem processes. Science,277, 1300-1302. Dr. John A. Finn University of Reading