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.