lecture 23 lecture notes

Biodiversity 2
Global Status and Threats Conservation Strategies
Past extinctions

• Five great extinctions
– 440 mya, 370 mya, 245 mya (Permian), 210 mya, 65 mya (K-T)
– Followed by adaptive radiations
• The sixth extinction
– Phase 1: began 100,000 years ago with spread of humans
– Phase 2: began 10,000 years ago with dawn of agriculture
– Phase 3: began 250 years ago with industrial and scientific revolutions
• Declines in biodiversity have long been associated with human populations. Large organisms are most at risk
Threats to biodiversity
• The Sextet of threats:
• Over-exploitation
• Exotic species
• Habitat destruction
– (degradation, fragmentation)
• Climate change
• Pollution
• Domino effects
IUCN rankings
• Critically endangered are those whose numbers have decreased or are expected to decrease by 80%, within three generations (3000 spp )
• Endangered species are at risk because of small population size or threatened habitat (5000 spp)
• Vulnerable (8000 spp)
• Hunting, especially commercial hunting and poaching, has driven many species to extinction
• Passenger pigeon for meat etc
• Bushmeat harvest is a crisis of tropical forests today
• Cod fishery – big example
Bushmeat trade
• For the tropical forests of central and west Africa (the Congo Basin rainforests), greatest threat to vertebrate species is over-hunting for subsistence and commerce
• For people living in these areas, up to 90% of total animal protein may be derived from wild animals
Non-indigenous species
• Non-indigenous species (NIS) Aka exotic, introduced, alien
• “Invasive”, “nuisance” is used for species that have strong negative impacts
• Nuisance is in the eye of the beholder (ex. Bass vs carp)
Zebra mussel case history
• they can have strong negative effects on native mollusks by fouling their shells and outcompeting them
• Due to their ability to filter 10-100% if the water column daily, they have transformed the Hudson River ecosystem
Nile Perch in Lake Victoria
• Non-indigenous species (invaders) often are more effective predators or competitors, thereby eliminating native species. Island (and lake) species may be especially vulnerable.
Causes of Spread of Aquatic NIS
• Colonial nostalgia: acclimation societies in NZ
– 20 of 46 species of fishes found in NZ are exotic
• Purposeful introductions for angling
– > 25% of recreational catch in US
• Fish culture escapees
• Pet trade
– More than 1,200 species currently, 6,000 potentially
– Hitch-hikers
• Inter-basin transfers
• Biocontrol
– Mosquitos: gambusia, guppy
– Weeds: tilapia, grass carp
What influences invasion success?
• Aspects of the invader
– Trophic, behavioral, physiological and life history traits
• Aspects of the receiving environment
– Habitat matching
– Environmental resistance
• Success rates appear to be high
– Of ~ 1,000 first introductions reported in Fishbase, 64% were successes
– Of 110 documented invasion of fishes into California, 57% were successes
California case study
• 68 native species, 110 documented non-native introductions, 43% failed
• best predictors of success:
– a past history of successful invasions (1:1 4:1)
– broad environmental tolerance
– ability to thrive in human-altered environments,
– similarity of source and recipient environments
– large propagule size (at least 100 individuals, multiple releases, or both).
NIS superstars
• Cyprinus carpio
• Oreochromis mossambicus
• Oncorhynchus mykiss
Habitat loss and fragmentation
• In addition to direct habitat loss, habitat fragmentation leaves habitat fragments too small to maintain viable populations, too fragmented to allow dispersal to have ‘rescue effect’
Global deforestation
• Obvious form of habitat loss
• Original tropical forest was ~15m km2; today it is about 8m km2
• At present rates of loss ~ 10% of the original tropical forests will remain by the end of the 21st century
As habitat shrinks in size….
• Populations of bighorn sheep living on semi-isolated mountain tops in the southwestern USA: Note that larger populations persist longer than smaller populations. All populations < 50 went extinct within 50 years.
Habitat fragmentation and disease dynamics
• Lyme Disease is a tick-borne disease prevalent in North America and Europe
• Forest fragmentation creates small habitat units that favor certain species
• The principal reservoirs, deer and the white-footed mouse, increase dramatically in abundance in fragmented habitats that contain low vertebrate diversity
Extinction rates
• “Species are now perishing at 1,000 times or even 10,000 times the ‘background’ extinction over the past 600 million years”
– Biologist Sir Robert May
• Background, mass, anthropogenic extinctions
• How can we know the probable rate of extinction?
– First, estimate the probable number of species
– Second, estimate rates of habitat loss
– Third, use the species-area relationship to estimate species loss
Estimating Rates of Species Loss
• The relationship between number of species and area of habitat is S = c A z
• the rate of loss of tropical forest from satellite imagery is 1-2% annually
• the resulting loss rate of species results in an overall loss of 25 - 50% of the world’s species by 2100
• Assuming tropical forests harbor 10 million species, this loss is 27,000/yr (and 3/hr)
Take-home messages
• Biodiversity is threatened by the “sinister sextet”
• Habitat loss represents the single biggest threat, followed by invasives
• But in the oceans and for bushmeat animals, over-harvest is more important
• Some 25-50% of the world’s biodiversity is likely to be lost by the end of the 21st century
How can we protect biodiversity?
• Protected lands
– What is the current extent of protected area?
– How does the level of protection vary among protected areas?
– How can we best determine where new protected areas are needed?
– How might we design nature reserves to maximize their effectiveness?
• But, protected lands comprise ~ 12% of the earth’s land area.
– Management of the remaining 85-90% must also be part of a biodiversity protection strategy
IUCN Protected Area Categories
• Category I. Strict Protection: strict nature reserve/wilderness areas. managed mainly for science or wilderness protection. Generally small
• Category II. Ecosystem Conservation and Tourism: national parks. Generally larger areas with outstanding features. Many visitors
• Category III. Conservation of Natural Features: natural monuments. usually smaller areas protecting a single spectacular natural feature.
• Category IV. Conservation Through Active Management: Areas managed to protect and utilize wildlife species.
• Category V. Landscape/Seascape Conservation and Recreation: Sometimes called protected landscapes/seascapes.
• Category VI. Sustainable Use of Natural Ecosystems: Protected areas managed mainly for the sustainable use of natural ecosystems.
Protected areas can be very effective
• well-selected protected areas can harbor a large share of a region’s biodiversity within a small land area
• Santa Rosa park covers 0.2% of Costa Rica’s land area, but contains 55% of 135 species of CR’s sphingid moths
Protected areas in Africa
• parks protecting 3-12% of land area of various countries may contain 70-90% of bird species
New Protected Areas
• Goal: increase extent of protected areas
– From ~12% to ~15% of Earth’s land surface, with representation by ecosystem type.
• Where should they be located?
– uniqueness, representation, endangerment
– hotspots and endemism
– gaps in the network of protected lands
• How should they be designed?
– size, shape, linkages, matrix
– Based on principles of population and community ecology, species-area relationships
Gap Analysis
• An approach based on mapping of vegetation, animals (usually terrestrial vertebrates) and land ownership in order to identify gaps in the protected areas network
• relies on three primary data layers:
– distribution of vegetation
– habitat association of terrestrial vertebrates with vegetation
– land ownership
The gap analysis process
• Determine where the species are located
• Compare them to where the protected areas are
• Use this information to identify where the conservation areas need to be
Using Gap Analysis, One can ask:
• What fraction of threatened species occurs within existing reserves?
• What fraction of each major vegetation type falls within existing reserves?
• Are areas of highest species richness found within existing reserves?
• Are areas of high endemism found within existing reserves?
Design of Nature Reserves
• Reserves must be of sufficient size to maintain large enough populations of all important species
• Reserves should protect at least several populations
• Reserves should minimize edge and fragmentation effects
• Reserves should consciously include the matrix of unprotected land in which they are embedded
Nature Reserves: Design Issues
• Reserves must be of sufficient size to maintain "large enough" populations of all important species.
• What is large enough? To maintain at least several hundred reproductive individuals. To include a viable population of the most wide-ranging species in it
• What are the important species? Any of conservation concern, keystone species, endangered species, economically important species, … perhaps all species?
• Reserves should protect at least several populations, with metapopulation structure (“ a set of sub-populations that are spatially distinct but have some migration between them”)
• corridors
• stepping stones
• Reserves should minimize edge and fragmentation effects.
• Round shapes minimize edge, elongated shapes maximize edge
• Avoid internal fragmentation due to logging, farming, roads, power lines, etc.
• Aggregate small areas into larger conservation blocks by including surrounding land to create a matrix of land enjoying high as well as low conservation protection status
• Reserves should consciously include the matrix of unprotected land in which they are embedded
• Form partnerships with public (agencies) and private (citizens) land owners
• Educate one another
• Establish mechanisms to resolve use conflicts
Costa Rica’s success story
Climate change threatens place-based conservation
• Will species migrate to new habitat?
• Is suitable habitat available?
• IS there a path along which to migrate?
• Will the community move as a unit?
• What is the role of “assisted migration”?
Take-away messages
• Protected areas worldwide cover about 12% of national land area
• Protected areas are managed for various objectives from strict nature protection to controlled harvest
• Gap analysis identifies gaps in the network of parks, reserves, and public lands
• Many factors influence the design and placement of reserves, including: size, metapopulation structure, edge and fragmentation effects, and linking of reserves to the surrounding land matrix

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