Principles of Conservation Biology: an Overview
Prof. Claire Kremen
Univ Cal Berkeley
Cal Academy Bioforum
Apr 4, 2009
Biodiversity Defined
• “Biodiversity is the total variety of life on earth. It includes all genes, species and ecosystems and the ecological processes of which they are a part” (Convention on Biodiversity, 1992)
Ecological interactions
Biodiversity is more than the sum of the parts
Interactions “structure” communities, maintain diversity, and make ecosystems work
e.g. Competition Predation Mutualisms (e.g. pollination, seed dispersal)
Evolution and extinction
• Biodiversity is not static but constantly changing
• 99% of the species that ever lived have gone extinct– Mass extinctions– Background
extinctions– Finite lifetimes
Conservation biology
• Concerned with loss of biodiversity, not just loss of species– “Fundamental loss of resources in
genetics, species, community attributes and ecosystem properties”
– Flip side: maintenance of biodiversity, ecological and evolutionary processes
Why care about biodiversity?
• Intrinsic value (Muir, 1838-1914)– All species have value independently of their
utility to humans• Utilitarian value (Pinchot, 1865-1946)
– Species that provide the “greatest good to the greatest number” (over the longest time) have value
• Cons Bio : (Leopold, 1886-1948)– can include both value systems– “To keep every cog and wheel is the
first precaution of intelligent tinkering" (Leopold 1943).
Aldo Leopold (1886-1948)Evolutionary-Ecological Land Ethic
• Biological communities: assemblages of interdependent species
• Maintaining the health of natural ecosystems and ecological / evolutionary processes
• Humans exist within the ecological community; depend on ecosystem services
• Synthetic approach:– Both intrinsic value and utilitarian value
Why be concerned about biodiversity loss if extinction is a fact of life?
Moderate certainty: current extinction rates > by 100 – 1000 times
10 – 30 % of mammals, birds and amphibians threatened
Is extinction outpacing speciation potential?
Major drivers of endangerment
From Wilcove 1996
What’s missing?
Threats to terrestrial species
• Terrestrial habitat loss• 39-50% of land surface transformation
Result of habitat loss
• Reduction in total area decrease in size, # of populations local extinctionsfewer species
• Reduction in habitat diversity– Reduced species diversity– Cascading effects, co-extinctions
Habitat fragmentation
• Above and beyond habitat loss
• Isolation: reduced immigration, re-colonization
• Edge effects
From Primack 2002
The forested areas of Warwickshire, England
Invasion
– The distribution of species on Earth is becoming more homogenous
– The rate of invasion is increasing over time
Growth in Number of Marine Species Introductions in North
America and Europe
HOMOGENIZATION
Introduced cheatgrass, Bromus tectorum, has transformed the Great Basin shrub-
steppe ecosystem • Has increased
fire frequency from once/80 years to once/4 years!
• Occupies over 5 million hectares of Great Basin
Climate change effects on biodiversity
• Range shiftsLatitudinal rangeAltitudinal range
• Mis-matched interactions• Reassembled (scrambled) communities• Feedbacks (e.g. vegetation and climate)• Species Endangerment
Climate change endangers polar bears
• Sea ice is the key– Bottom up: habitat for
micro-algae– Top down: seal
hunting ground; corridors to dens
• Loss of sea ice endangers polar bear
• Loss of top predator: cascading effects on Arctic food web
Climate change can induce coral reef bleaching
http://www.ogp.noaa.gov/misc/coral/98bleaching/
Bleached and normally pigmented Pocillopora colonies
Oceans and Freshwater Aquatic habitats
• If anything are more vulnerable to same threats, with enhanced vulnerability to over-exploitation and pollution
• Freshwater– USA: Very high endangerment levels in fish &
amphibians (25-40%) and crayfish & molluscs (> 60%) compared to terrestrial vertebrates (15-18%
Over-exploitation of global ocean fisheries
• > 60% of the world’s fisheries are fully to over exploited, or depleted
• By-catch increases fish-catch by 30%
Botsford 1997
Conserving biodiversity
• Genetic level: seed, egg, sperm banks
• Population and species level – science of managing small populations– Captive breeding (zoos/botanical gardens)– Reintroductions– Population management in the wild
• Protection (hunting, disease, habitat)• Genetic management (translocations)• Habitat restoration
Conserving biodiversity: habitat, species, ecosystem level
• Protected areas
• Managing the matrix– Restoration– Wildlife-friendly agriculture
Protected areas for Biodiversity Conservation
• Select the areas that represent and maintain biodiversity over time…
(Margules and Pressey 2000)
REPRESENTATION
Including as many different ecosystems and species in the reserve network
Representing the full range of variation (genetic, ecological) present within target species
Reserve Design Decision-Support
• Computer programs
• Meet conservation targets (e.g. conserve 20% of each habitat type and 3 populations of each species) at least cost
A network of reserves that represents species efficiently
• But it may not be so good at maintaining biodiversity – why not?
Site selection in the Sierra Nevada foothills for conservation prioritization
Grey = already protected
Maintaining biodiversity over time
• Population persistence (viability)• Maintaining ecological processes
– E.g. migrations
• Maintaining evolutionary processes– Potential for adaptation within populations
(genetic diversity)– Selecting areas where rapid speciation is
occurring
• Response to climate change
SIZE
CONNECTIVITY
Shape
Edge to area ratio
Corridors
Environmental gradients
Disturbance regime
Functional units
Matrix habitat
Reserve design features for persistence
SIZE Larger size • More species (interactions, functions), S-A relationship• More habitats (interactions, functions)• Larger populations – • Protects vulnerable species
– Area demanding: large-bodied, high-trophic level, rare– Habitat specialists (if habitat included)– Species requiring multiple habitat types
• Shape Reduced edge/area ratio, edge effects• Disturbance regime: maintenance of disturbance-generated
patch heterogeneity• Includes whole functional units• Includes whole environmental gradients
SIZE & EDGE EFFECTS
From Primack 2002
Edges create core versus edge habitat
Example: many songbirds experience high nest predation near edges in woodlots within sub-urban areas
Shape and edge
effects
Meffe & Carroll 1997
DISTURBANCE REGIME
• Disturbance promotes habitat heterogeneity– By resetting successional sequence in
parts of the landscape– Creating patchiness in the landscape
which is determined by the temporal and spatial scale of the disturbance(s)
Spatial and temporal scale of disturbance varies by type
SIZE & DISTURBANCE REGIME
• Disturbance promotes habitat heterogeneity– mosaic of patches at different successional stages
• Habitat heterogeneity:– supports species requiring multiple habitat types– Supports early successional species (e.g. Heath
fritillary butterfly = “Woodman’s follower”)
• Size of reserve ideally as big as or bigger than scale of likely disturbances
Functionally inter-dependent ecosystems:e.g. “a complex, dynamic patchwork of mangroves, sea grass bed and reefs” (Moberg & Ronnback 2003)
SIZE & FUNCTIONAL UNITS
SIZE: Bigger is better!
CONNECTIVITY
Shape
Edge to area ratio
Corridors
Environmental gradients
Disturbance regime
Functional units
Matrix habitat
Reserve design features for persistence
CONNECTIVITY
• Isolation is a key factor causing loss of species from reserves– Preventing gene flow, maintenance of genetic diversity– Reducing recolonization following extinction (rescue
effect)– Preventing access between summer/winter grounds
for migratory species– Preventing access to multiple habitat types needed for
different life stages– Preventing response to global warming
CONNECTIVITY: Multi-scale responses
PROBLEM of FRAGMENTATION – Preventing gene flow, maintenance of genetic diversity– Reducing recolonization following extinction (rescue effect)
– Preventing access between summer/winter grounds for migratory species
– Preventing access to multiple habitat types needed for different life stages
– Preventing response to global warming
RESPONSE
•Create corridors between reserves•Manage the matrix around reserves
Wildlife overpass
Transportation Equity Act for the 21st Century provides funding
http://www.fhwa.dot.gov/environment/wildlifecrossings/overview.htm
Managing the Matrix
Making matrix “friendly” to wildlife -- Reserve zonation: core, buffer, transition
-- Wildlife friendly farming/Restoration
CONNECTIVITY: Multi-scale responses
PROBLEM of FRAGMENTATION – Preventing gene flow, maintenance of genetic diversity– Reducing recolonization following extinction (rescue effect)
– Preventing access between summer/winter grounds for migratory species
– Preventing access to multiple habitat types needed for different life stages
– Preventing response to global warming
RESPONSE
•Create corridors between reserves•Manage the matrix around reserves
Protect migratory routes/stop-overs
Stop-over sites along songbird migration routes
• Neotropical birds• Use radar to detect
nocturnal bird movement– Timed to get
departure events from stopover points (20-40 min after sunset)
– Signal characteristics
Breeding
wintering
http://www.njaudubon.org/Education/Oases/RadImages.html
CONNECTIVITY: Multi-scale responses
PROBLEM of FRAGMENTATION – Preventing gene flow, maintenance of genetic diversity– Reducing recolonization following extinction (rescue effect)
– Preventing access between summer/winter grounds for migratory species
– Preventing access to multiple habitat types needed for different life stages
– Preventing response to global warming
RESPONSE
•Create corridors between reserves•Manage the matrix around reserves
Protect migratory routes/stop-overs
•Include whole functional units, disturbance regimes, environmental gradients within reserves or reserve networks
•Include elevational or latitudinal gradients within reserves
•Habitat heterogeneity – connectedness between habitats, marine and terrestrial•Species response to climate change: Include elevational gradients within reserve
Masoala, Madagascar
Designing Masoala National Park, Madagascar
New Reserve Design Methods
• Represent species or habitats efficiently
• Minimize edge effects, maximize clustering
• Maximize connectivity
Leslie et al. 2003 Ecol App.
Conclusions• Biodiversity has great value, both
intrinsically, and also because human life depends on it
• But, it is under threat, from habitat loss and degradation, invasive species, climate change, pollution and over-exploitation
• Conservation biologists have many tools to protect biological diversity, from genetic to ecosystem levels.
Conclusions• Protected areas are an important tool for
biodiversity conservation.• The design of protected areas and reserve
networks should foster representation of biodiversity and its persistence.– Reserves need to be sited efficiently to represent
biodiversity.– Size, shape and connectivity of reserves and
relationship with the surrounding landscape matrix are essential considerations for biodiversity persistence.