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

Dr. John A. Finn University of Reading 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 Human population in the biodiversity hotspots. z25 biodiversity hotspots that have exceptionally high species richness and endemicity. Are also very threatened by human activities. ( Cincotta et al. Nature 404: ) zOverhead- indicates relationship between biodiversity hotspots and population pressure

Dr. John A. Finn University of Reading z“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 References for previous section: zBiological diversity, ecosystems and the human scale Folke et al. Ecological Applications 6: (electronically available through library)  Causes, consequences and ethics of biodiversity Tilman, D. Nature 405: (electronically available through registration at Nature website html ) zHuman population in the biodiversity hotspots. Cincotta et al. Nature 404:

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

Dr. John A. Finn University of Reading "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 ) 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] Experimental reductions in biodiversity

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

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

Dr. John A. Finn University of Reading What are ecosystem effects of a reduction in diversity? zRivet: 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. Ecosystem function Species richness low high

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

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

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

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

Dr. John A. Finn University of Reading Decreasing species richness (log 2 scale)

Dr. John A. Finn University of Reading zThe 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

Dr. John A. Finn University of Reading zThe 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 Explanations for differences between single sites and meta-analysis z(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 z(ii) sites do differ in their responses, but the overall analysis is not powerful enough to reveal a significant location-by-species richness relationship z(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

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

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

Dr. John A. Finn University of Reading How might biodiversity relate to ecosystem function? z2. Niche complementarity- ecological differences between species lead to more complete utilisation of available resources in more diverse communities. yGranivorous ants/rodents feeding on different sized seeds; microhabitat preferences in animals yDifferent rooting depths by plants, different degrees of shade- tolerance etc. z3. Mutualisms- A reduction in positive mutualistic interactions among species in more depauparate and simplified communities.

Dr. John A. Finn University of Reading FG 2 FG 3 FG 1 SP 1 SP 2 SP 3 SP 4 Niche complementarity: Within- and between- FG diversity 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

Dr. John A. Finn University of Reading Environmental fluctuation 6 spp1 spp 7 spp 1 spp Stable conditions The insurance hypothesis: More diverse assemblages will have a greater probability of having species that are adapted to changed conditions Contribution of each species to ecosystem function Species richness

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

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

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