Chapter 11 Topics
Earth’s biodiversity
Biodiversityloss/extinction
Causes of biodiversityloss
The benefits ofbiodiversity
Conservation biology
Conservation of species
Conservation above thespecies level
Levels of biodiversity
Biodiversity = varietyof life at all levels oforganization
Species diversity
Genetic diversity
Population andcommunity diversity
Species diversity
Species diversity = thenumber or variety ofspecies in a particularregion
Richness = the number ofdifferent species
Evenness = the similarityin numbers betweenspecies
Speciation adds tospecies richness
Genetic diversity
Encompasses differences in DNA among individuals
The raw material for adaptation to local conditions
Populations with higher genetic diversity can survive
Populations with low genetic diversity arevulnerable to environmental change or disease
Inbreeding depression = genetically similar parentsmate and produce inferior offspring
Ecosystem diversity
Ecosystem diversity =number and variety ofecosystems, communities,habitats in an area
Includes considerationof landscape ecologyconcepts – the sizes,shapes, spatialdistribution, andconnections amongpatches
Taxonomic framework
Recall that biological organism are classified in avariety of taxonomic levels based on certain keycharacteristics
Uneven species distribution
Species are not evenlydistributed amongtaxonomic groups
Insects predominate overall other life-forms
40% of insects = beetles
Groups accumulatespecies by:
Adapting to localconditions
Allopatric speciation
Low rates of extinction
Variation across groups
Measuring biodiversity
1.8 million species have been identified/described
Best estimate of the number of species = 14 million(could be 3 million, could be 100 million)
It is very difficult to know how many species exist
Small organisms are easily overlooked
Many species look identical until thoroughly examined
Many remote spots on Earth remain unexplored
Entomologist Terry Erwin found 163 beetle speciesliving on one tree species
Biodiversity is unevenly distributed
Living things are notdistributed evenly onEarth
Latitudinal gradient =species richness increasestoward the equator
Canada has 30–100species of breedingbirds, while Costa Ricahas more than 600species
Causes of longitudinal gradient
High plant productivity
Climate stability
More niches
Species coexistence
Diverse habitats increasespecies diversity andevenness
Human disturbance canincrease habitat diversitybut only at the local level
Biodiversity loss and extinction
Extinction = occurs when the last member of aspecies dies and the species ceases to exist
Extirpation = the disappearance of a populationfrom a given area, but not globally
Extinction is a natural process – 99% of all speciesthat ever lived are now extinct
Background rate of extinction = natural extinctions
The background rate of mammal or marine species:each year 1 species out of 1–10 million goesextinct
Current rates exceed background
The current extinction rate is 100 to 1,000 timesgreater than the background rate
This rate will increase tenfold in future decades dueto human population growth and resourceconsumption
The Red List = species facing high risks of extinction
Mammal species (21%), bird species (12%)
17–74% of all other species
In the U.S., in the last 500 years, 237 animal and30 plant species have been confirmed extinct butthe actual numbers are undoubtedly higher
Causes of biodiversity loss
The reasons for biodiversity loss in specific situationscan be hard to determine because multiple factorsoften interact in complex ways
Four primary causes of population decline are:
Habitat alteration
Invasive species
Pollution
Overharvesting
Global climate change now is the fifth cause
Habitat alteration
Habitat alteration – greatest cause of biodiversity loss
Habitat alteration encompasses
Habitat destruction
Habitat fragmented
Habitat degradation
Examples include
Farming simplifiesecological communities
Grazing modifiesgrassland structure
Clearing forestsremoves resources
Habitat fragmentation
Habitat fragmentation =gradual, piecemealdegradation of habitat
Continuous habitats arebroken into patches
Species needing thathabitat disappear
Landscape-levelstrategies try to optimizeareas to be preserved
Invasive species
Introduction of non-nativespecies to new areas
Accidental: zebra mussels,weeds
Intentional: food crops,exotic pets, ornamentalplants
Island species areespecially vulnerable
Invaders lack naturalpredators, competitors, orparasites
Pollution
Pollution harms organisms in many ways
Air pollution degrades forest ecosystems
Water pollution impairs fish and amphibians
Agricultural runoff harms terrestrial/aquatic species
Toxins/garbage/oil/chemicals impact organisms
Overharvesting
Vulnerable species: K-selected
Large, few in number,long-lived, and havefew young
Powerful economicincentives increasepoaching
Human manipulation of Earth’s climate system hasglobal impacts on biodiversity
Emission of greenhouse gases warms temperatures,modifying global weather patterns
The frequency of extreme weather events increases
Increased stress forces organisms to shift theirgeographic ranges
Most animals and plants will not be able to adapt
20–30% of species are at increased risk of extinction
Climate change
Biodiversity loss concept map
Biodiversity ecosystem services
Provides food, fuel, fiber, and shelter
Purifies air and water and detoxifies wastes
Stabilizes climate, moderates floods, droughts, wind,temperature
Cycles nutrients, renews soil fertility
Pollinates plants and controls pests and disease
Maintains genetic resources
Provides cultural and aesthetic benefits
Allows us to adapt to change
Biodiversity ecosystem function
It increases stability and resilience of naturalsystems
Decreased biodiversity reduces a system’s ability tofunction and provide services to our society
The loss of a species affects ecosystems differently
If the species can be functionally replaced by others, itmay make little difference
Loss of keystone species, ecosystem engineers, or toppredators causes other species to decline or disappear
“To keep every cog and wheel is the first precautionof intelligent tinkering” (Aldo Leopold)
Biodiversity food security
Industrial agriculture has narrowed our diet
Wild and rare species can improve food security
New potential food crops are waiting to be used
Serendipity berry is 3,000 times sweeter than sugar
Genetic diversity within crops is enormouslyvaluable
Turkey’s wheat crops received $50 billion worth ofdisease resistance from wild wheat
Wild strains provide disease resistance
Many grow back year after year without beingreplanted
Biodiversity medicines
Wild species produce$150 billion/year ofdrugs
Taxol comes from thePacific yew tree is usedto treat cancer
Every species that goesextinct is a lostopportunity to curedisease
Biodiversity economic benefits
Biodiversity generates income through tourism,especially in developing countries
Costa Rica: rainforests
Australia: Great Barrier Reef
Belize: reefs, caves, and rainforests
Tanzania: savanna wildlife
A powerful incentive to preserve natural areas andto reduce impacts on the landscape and species
Too many visitors to natural areas can degrade theoutdoor experience and disturb wildlife
Conservation biology
Conservation biology = studies the factors behindthe loss, protection, and restoration of biodiversity
An applied and goal-oriented science
Conservation biologists
Integrate evolution, extinction, ecology, andenvironmental systems
Design, test, and enact ways to decrease our impacts
Study genetic attributes of organisms to infer the statusof their populations
Determine how small a population can become beforeit runs into problems
Endangered species
Endangered Species Act (ESA) (1973) = theprimary U.S. legislation for protecting biodiversity
It forbids the government and citizens from takingactions that destroy endangered species or theirhabitats or trading in products made fromendangered species
The ESA’s goal is to prevent extinction
By stabilizing declining populations
Thus enabling populations to recover
ESA has been successful
In 2010, the U.S. had 1,010 species listed asendangered and 314 listed as threatened
Intensive management has saved/stabilized species
40% of declining populations are now stable
Peregrine falcons, brown pelicans, bald eagles, andothers have recovered and are no longer listed
These successes occur despite problems
Underfunding of the U.S. Fish and Wildlife Service andthe National Marine Fisheries Service
Recent political forces have tried to weaken the ESA
ESA is controversial
Many Americans supportprotecting endangeredspecies
Opponents feel that theESA values endangeredorganisms more than thelivelihood of people
Habitat conservation plansand safe harboragreements allowlandowners to harmspecies if they improvehabitat for them in otherplaces
International conservation efforts
UN Convention on International Trade inEndangered Species of Wild Fauna and Flora(1973)
CITES protects endangered species by banninginternational transport of their body parts
Convention on Biological Diversity (1992)
Seeks to conserve biodiversity, to use biodiversity in asustainable manner, and to ensure the fair distributionof biodiversity’s benefits
By 2010, 193 nations had signed on to the Convention;only Andorra, the Vatican, and the U.S. did not join
Tools: captive breeding
Captive breeding =individuals are bred andraised so they can bereintroduced into the wild
Reintroductions can becontroversial
Ranchers opposedreintroducing wolves toYellowstone National Park
Fragmented habitat mustbe improvedbefore releasing animals
Tools: forensic approaches
Forensic science (forensics) = analyzes evidence toidentify or answer questions relating to a crime
Conservation scientists use forensics to protectspecies
Researchers use DNA to identify a species orsubspecies and its geographic origin
Detecting illegal activity helps enforce lawsprotecting wildlife
Tools: “umbrellas” and “flagships”
Conservation biologists sometimes use particularspecies to conserve communities and ecosystems
Umbrella species = species that, when protected,also help protect other, less charismatic species
Often large species that need large amounts of habitat
Protecting their habitat automatically protects others
Flagship species = large and charismatic species,such as the World Wildlife Fund’s panda bear, areused as spearheads for biodiversity conservation
Tools: parks and preserves
Setting aside land in parks and preserves conserveshabitats, communities, ecosystems, and landscapes
12% of the world’s area is in parks, wilderness,reserves, etc.
But these areas are not all managed forbiodiversity
Some are used for recreation, water protection
Some are also illegally logged
Many are not large enough to preserve whole systems
Tools: biodiversity hotspots
Biodiversity hotspots =regions with very highbiodiversity in a smallarea
Area must have at least1,500 endemic plantspecies
Area must have lost70% of its habitat dueto humans
Global distribution of hotspots
2.3% of the planet’s land surface contains 50% ofplant species, 42% of terrestrial vertebrate species
Tools: economic strategies
Debt-for-nature swap = a conservation organizationpays off part of a developing country’s internationaldebt
In exchange, the country sets aside money to fundenvironmental education and manage protected areas
The U.S.’s Tropical Forest Conservation Act covered$218 million in debt payments for 13 developingcountries
Conservation concession = conservation organizationspay nations to conserve, and not sell, resources
Tools: local engagement
Developing nations often do not supportconservationists from developed nations trying topreserve areas
Community-based conservation = conservationistsengage local people to protect land and wildlife byproviding education, health care, and developmentaid
People are retrained
Income is supplemented
Poaching is reduced
The bottom line…
What’s the best way to safeguard biodiversity andnatural systems?
Protect natural areas, the habitats they contain, andthe communities they support before they aredestroyed, fragmented, or degraded