Biodiversity and Ecosystem FunctionEcosystems Ecology April 9th, 2014

Biodiversity loss and its impact on humanityBradley J. Cardinale, J. Emmett Duffy, Andrew Gonzalez, David U. Hooper, Charles Perrings, Patrick Venail, Anita Narwani, Georgina M. Mace, David Tilman, David A.Wardle, Ann P. Kinzig, Gretchen C. Daily, Michel Loreau, James B. Grace, Anne Larigauderie, Diane S. Srivastava & Shahid Naeem

Nature Review- June 2012

Biodiversity The variety of life Variation among species, functional traits

and genes Measured as:

Richness- the number of unique life forms Evenness- the equitability among life forms Heterogeneity- dissimilarity among life

forms Phylogeny Distance

Ecosystem Function Ecological processes that control the

fluxes of energy, nutrients and organic matter through an environment

Examples include: Primary production Nutrient cycling Decomposition Habitat building

Assume this is related to biodiversity

BEF Questions Is there more plant biomass in a more

diverse or less diverse plot of land? Do diverse forest store more carbon than

less diverse forests? Can a stream clean up more pollution if it

has a more diverse microbial community vs. a less diverse microbial community?

Do more diverse fisheries provide more food than less diverse fisheries?

Biodiversity Research at Cedar Creekhttps://www.youtube.com/watch?v=WmqyY4BXJaI

Six Consensus Statements Loss of biodiversity reduces ecosystem functions Biodiversity enhances ecosystem stability BEF relationship is positive and decelerating Biodiversity increases ecosystem function

through the sampling effect and complementarity

Trophic interactions are important to the BEF relationship

Which species are lost matters to ecosystem function

Consensus Statement One Loss of biodiversity reduces ecosystem function Biodiversity ↓

Capture of resources ↓ Biomass production ↓ Decomposition ↓ Nutrient recycling ↓

Loss of biodiversity can be: Genes Species Functional groups

There are exceptions to this general statement

Evidence of BEF relationship and exceptions

O’Connor and Byrnes 2013

Consensus Statement Two Biodiversity increases stability of ecosystem

functions over time Mechanisms enhancing stability:

Over-yielding: mean biomass increases with diversity more rapidly than its standard deviation

Statistical averaging: random variation in the abundances of different species reduces the variability of aggregate ecosystem variables

Compensatory dynamics: competitive interactions and/or differential responses to environmental fluctuations among different species leads to asynchrony in their response to the environment

Statistical Averaging

O’Connor and Byrnes 2013

Compensatory Dynamics

Lennon and Jones 2011

Consensus Statement Three Relationship between biodiversity

and ecosystem function: Positive Nonlinear Saturating

Initial losses of biodiversity has relatively small impacts, but increasing losses lead to accelerating decrease in function Do not know inflection point

BEF Relationship

Cardinale et al 2011

Positive, nonlinear,decelerating curve with asymptote

Consensus Statement Four Mechanisms behind BEF

relationship: Sampling effect: increased biodiversity

increases chances of including highly productive species

Complementarity: coexisting species either positively interact or use different resources/ niches and therefore use resources more completely

Sampling Effect

Tilman et al 1997

Complementarity: Niche Partitioning

Tilman et al 1997

A Tale of Two Urchinshttp://www.nytimes.com/video/science/100000002735051/creaturecast-a-tale-of-two-urchins.html?playlistId=100000002438160

Consensus Statement Five Loss of diversity across trophic levels

has the potential to influence ecosystem functions even more strongly than diversity loss within trophic levels

Food web interactions are key mediators of ecosystem functioning

Loss of higher consumers can cascade through a food web to influence plant biomass

Trophic Levels and Biodiversity Loss

O’Connor and Byrnes 2013

Trophic Levels and Biodiversity Loss

Jackson et al 2001

Consensus Statement Six There is considerable variation in the

relationship between biodiversity and ecosystem function Some of this variability comes from

differences in the identity of the organisms and their functional traits

To predict the consequences of extinction we must know which species have greatest extinction risk and how the traits of those organisms influence function

Random vs. Ordered Loss

O’Connor and Byrnes 2013

Four Emerging Trends Biodiversity loss may be as large an

environmental threat as climate change Biodiversity loss may have a larger impact

when examined on larger spatial and temporal scales

More biodiversity is needed to maintain multiple functions than is needed to maintain a single function

Phylogenetic diversity may be an important measure of biodiversity

Emerging Trend One The impacts of biodiversity loss might

be sufficiently large to rival the impacts of many other global drivers of environmental change

Because the BEF relationship is nonlinear the exact ranking of diversity relative to other drivers will depend on the magnitude of biodiversity loss, as well as magnitudes of other environmental changes

Diversity Loss vs. Environmental Change

Tilman et al 2012

Emerging Trend Two Diversity effects are stronger:

Over longer time scales With larger spatial scales

Diversity effects in small-scale, short-term experiments may underestimate the impacts of diversity loss on the functioning of more natural ecosystems

More environmental heterogeneity may increase opportunities for species to exploit more niches

Increased Biodiversity Effect Over Time

Tilman et al 2001

Emerging Trend Three Maintaining multiple ecosystem

processes at multiple places and times requires higher levels of biodiversity than does a single process at a single place and time

Organisms that control ecological processes at any single location, or in any particular year, often differ from those that control processes in other locations or years

Biodiversity and ecosystem multifunctionality

Hector and Bagchi 2007

Emerging Trend Four The ecological consequences of

biodiversity loss can be predicted from evolutionary history

Species contain genetic and trait variation that is shaped by patterns of ancestry

Phylogenetic distances among species may explain more variation in biomass production than taxonomic diversity

Importance of Phylogenetic Diversity

Flynn et al 2011

Ecosystem Services The suite of benefits that ecosystems

provide to humanity Two types of ecosystem services

Provisioning- involve the production of renewable resources

Regulating- services that lessen environmental change

What does biodiversity do for us?https://www.youtube.com/watch?v=e-Ik1VVgQvo

Four BES Statements Biodiversity is often associated with

increased ecosystem services Biodiversity can have a mixed

association with ecosystem services For many ecosystem services there is a

lack of evidence relating its relationship to biodiversity

Biodiversity can have a negative association with ecosystem services

Statement One Biodiversity directly influences or is

strongly correlated with certain provisioning and regulating services

Most of these services can be directly linked to the ecosystem functions measured in BEF experiments

For services less tightly linked to ecosystem functions, we often lack rigorous verification of the diversity–service relationship

Biodiversity and Ecosystem Service

Cardinale et al 2011

Statement Two For many ecosystem services the

evidence for effects of biodiversity is mixed

Important opportunities exist for new research to assess the factors that control variation in the response of these services to changes in biodiversity

Biodiversity and Ecosystem Service

Cardinale et al 2012

Statement Three For many services there are

insufficient data to evaluate the relationship between biodiversity and ecosystem service

This may be attributable to different uses of the term biodiversity

This emphasizes the need for stronger and more explicit evidence to back up claims for biodiversity effects on ecosystem services

Statement Four For a small number of ecosystem

services, current evidence for the impact of biodiversity runs counter to expectations

There are instances where increased biodiversity may be deleterious

Cautions against making sweeping statements that biodiversity always brings benefits to society

Biodiversity and Ecosystem Service

Cardinale et al 2012