Biomes and Biodiversity
Objectives
• Recognize the characteristics of major biomes and understand the most
important factors that determine their distribution
• Describe characteristics of aquatic ecosystems
• Describe the ways in which humans damage these ecosystem types
Objectives
• Define biodiversity, explain its importance and describe its status
• Describe how human activities cause biodiversity loss
• Identify regions and ecosystems of high biodiversity
• Evaluate the effectiveness of efforts to protect endangered species
Terrestrial biomes
• Biomes - Areas sharing similar climate, topographic and soil conditions, and
roughly comparable communities
• Most terrestrial biomes are identified by the dominant plants
– Temperature and precipitation are among the most important determinants
in biome distribution
Deserts
• Characterized by low moisture levels and precipitation that is infrequent and
unpredictable
• Wide daily and seasonal temperature fluctuations
• Plants and animals exhibit water conservation characteristics
Deserts
• Soils are easily disturbed by human activities and slow to recover
• Subject to overgrazing
Grasslands
• Communities of grasses, seasonal herbaceous flowering plants, and open
savannas
• Few trees due to inadequate rainfall
• Large daily and seasonal temperature fluctuations
Grasslands
• Frequent grass fires
• Historic grazing by roaming herds of large ungulates
• Historic conversion to farmland
• Overgrazing a threat to remaining grasslands
Savanna
• Grassland with trees
• A bit more precipitation than grasslands
• Frequent fires
Tundra
• Arctic tundra and alpine tundra
• Very short growing season, with cold harsh winters
• Water locked up much of the year.
• Most animals migrate south or downhill in winter.
• Low biological productivity and low diversity
• Treeless
Tundra
• Damage slow to heal
• Global warming threatens tundras
• Air pollution accumulates at high latitudes
• Oil and gas drilling
Conifer forests
• Cone-bearing
• Plants reduce water loss by evolving thin, needle-like evergreen leaves with
thick waxy coating
• Fire often plays role in maintenance
• Can grow on nutrient-poor soils
• Humans rely on conifer forests for forest products
Conifer forests
• Southern Pine Forest in United States
• Boreal Forest - Northern Conifer Forest
– Broad band of mixed coniferous and deciduous trees between 45° and 60°
N latitude
– Moist and cool climate with abundant streams and wetlands
• Taiga - Northernmost edge of boreal forest
– Species-poor
– Harsh climate limits productivity
Temperate rainforest
• Wettest portion of coniferous forests of Pacific Northwest
• Mild temperatures, and very abundant precipitation. (>250 cm)
– Canopy condensation is major form of precipitation
Broad-leaved deciduous forest
• Temperate regions support lush summer plant growth when water is plentiful
– Deciduous leaves an adaptation to freezing temperatures and drought
• Rich variation of tree species
– Forest canopy covers diverse understory
•
Eastern half of US was covered with broad-leaved deciduous forest when
European settlers arrived
– Much of that was harvested a century ago for timber
– Now large areas have re-grown and are again approaching old-growth
status
Mediterranean
• Characterized by warm, dry summers and cool, moist winters
• Fires are a major factor in plant succession
– Referred to as chaparral in California
• Biodiversity hotspot threatened by human development
– Referred to as thorn scrub in Africa
Tropical moist forests
• Humid tropical regions support one of most complex and biologically rich
biomes
• Ample rainfall and uniform temperatures
Cloud forests
Tropical moist forests
• Tropical Rainforests - More than 200 cm annual rainfall with warm-hot
temperatures year-round
– 90% nutrients tied up in living organisms
– Rapid decomposition and nutrient cycling
– Thin soil cannot support continued cropping and cannot resist erosion
Tropical seasonal forests
• Semi-evergreen and partly deciduous forests tending toward open woodlands
and grassy savannas
– Characterized by distinct wet and dry seasons with hot temperatures yearround
– Less than 1 percent remain undisturbed
Marine ecosystems
• Salt water ecosystems
• Phytoplankton support marine food webs
• Productivity greatest near coastlines
• Currents distribute nutrients and organisms
• Deep areas of ocean depend on “marine snow” as primary nutrient source
Marine ecosystems
• Vertical stratification is an important aspect of many marine ecosystems
– Organisms tend to form distinctive vertical sub-communities
• Benthic - Bottom sub-community
– Low oxygen levels
• Pelagic - Water column
Open ocean
• Called a biological desert due to low productivity
• Some areas are productive
– Equatorial Pacific Ocean
– Antarctic Ocean
– Sargasso Sea
– Deep sea thermal vents
Coral reefs
• Coral Reefs - Accumulated calcareous skeletons of colonial organisms (coral)
– Depth limited by light penetration
• Corals have mutualistic relationship with algae
– Among most endangered communities
• Dynamite fishing
• Global warming – coral bleaching
• Cyanide fishing
Mangrove forests
– Mangrove trees grow in salt water
– Occur along calm, shallow, tropical coastlines
– Threatened by forestry
– Protect and stabilize coastlines
Tidal Environments
• Estuaries - Bays or semi-enclosed bodies of brackish water that form where
rivers enter the ocean
• Important for fish and shellfish reproduction
Barrier Islands
• Barrier Islands - Low, narrow, sandy islands that form offshore from a coastline
– Protect inland shores from surf
– Prized for human development
• Loss of vegetation triggers erosion
Freshwater ecosystems
• Usually called aquatic ecosystems
• Less extensive than marine systems
• Centers of biodiversity
• Aquatic ecosystems are greatly influenced by surrounding terrestrial
ecosystems
Freshwater ecosystems
• Lakes
– Non-flowing water
– Freshwater lakes have distinct vertical zones separated by temperature
•
Rivers
– Flowing water
Wetlands
• Land surface is saturated or covered with water at least part of the year
• Water usually shallow enough to allow full sunlight penetration
• Trap and filter water - “nature’s kidney’s”
• Provide flood control
Human disturbance
• By some estimates, humans use about 40% of net terrestrial primary
productivity
• Temperate broad-leaved deciduous forests are the most completely humandominated biome
• Tundra and Arctic Deserts are the least disturbed
• About half of all original wetlands in the US have been degraded over the past
250 years
– 90% in Ohio
What is biodiversity?
• Biodiversity exists at several scales
– Genetic diversity - Measures variety of different versions of same genes
– Species diversity - Measures number of different kinds of organisms within
a community
– Ecological diversity - Measures richness and complexity of a community
What is a species?
• There are several different definitions for species
• We will define species in terms of reproductive isolation
– A species is all the organisms potentially able to breed in nature and
produce fertile offspring
How many species are there ?
• Currently 1.7 million species identified
• Estimates range between 3-50 million
– May be 30 million insect species
– Invertebrates make up 70% of all known species, and probably most of yet
to be discovered species
Where is biodiversity high?
• Only 10-15% of species identified are found in North America and Europe
• Greatest concentration of species in tropical rainforests and coral reefs
• Biodiversity hotspots
– Have exceptional numbers of endemic species
– Endemic species are those species that are found nowhere else
Biodiversity hotspots
Benefits of biodiversity
• Food
– As many as 80,000 edible wild plant species could be utilized by humans
Benefits of biodiversity
• Drugs and medicines
– More than half of all prescriptions contain some natural product
– Pharmaceutical companies actively prospect tropical countries for products
Ecological benefits
• Soil formation, waste disposal, air and water purification, nutrient cycling, solar
energy absorption, and biogeochemical and hydrological cycles all depend on
biodiversity
• Total value of these services are $33 trillion per year
– Can a system function without all its integral parts?
Watershed protection in the Catskills
• Water supply for New York City
• Worked with local farmers to reduce non-point pollution and preserve land
• Saved billions of dollars by performing watershed protection rather than
building a treatment plant
Aesthetic and cultural benefits
• Cultural diversity inextricably linked to biodiversity
Aesthetic and cultural benefits
• USFWS estimates Americans spend $104 billion annually on wildlife-related
recreation (compare to $81 billion on new automobiles)
• Ecotourism can be an important form of sustainable economic development
• Existence (intrinsic) value
Threats to biodiversity
• Extinction - Elimination of a species
– Natural Causes
• In undisturbed ecosystems, background rate appears to be one species
per decade
– In this century, human impacts have accelerated that rate, causing
perhaps thousands of extinctions annually
Natural extinction
• Fossil record suggests more than 99% of all species ever in existence are now
extinct
– Most went extinct before humans arrived
• End of Cretaceous - Dinosaurs and 50% of existing genera disappeared
• Permian period - Two-thirds of all marine species and nearly half of all
plant and animal families died out
• Many believe we are now in 6th mass extinction
HIPPO
• Habitat destruction
• Invasive species
• Pollution
• Population of humans
• Overharvesting
Human-caused reductions in biodiversity
• Habitat destruction
– Biggest reason for current increase in extinction is habitat loss
• Habitat fragmentation divides populations into isolated groups more
vulnerable to extinction
Population Viability Analysis (PVA)
• Minimum viable population size is number of individuals need for long-term
survival of rare and endangered species
Human-caused reductions in biodiversity
• Invasive species
– Invasive (exotic) organisms thrive in new territory where they are free of
usual predators, diseases, or resource limitations that limited them in
original habitat
– Rate of movement has increased in recent years
Invasive species
– Over past 300 years, 4,500 non-native species have become naturalized in
the U.S.
• 15% of these cause environmental damage
– Invasive species cost $138 billion annually in U.S.
Eurasian milfoil
• Arrived with shipping industry
• Forms dense colony
• Spread by boating activities
• Native weevil as possible biocontrol
Asian tiger mosquitoes
• Arrived on container ships carrying used tires
• Spread West Nile Virus
Zebra mussels
• Arrived in 1985 via ballast water
• Reach enormous densities
• Cover spawning beds
• Smother native mollusks
• Clog water intake pipes
Human-caused reductions in biodiversity
• Pollution
– Pesticides
– Lead
Human-caused reductions in biodiversity
• Population
– Human population growth
• Resource use
Human-caused reductions in biodiversity
• Overharvesting
– Passenger pigeon
– Bison
– Marine animals
– Bushmeat
Human-caused reductions in biodiversity
• Commercial products and live specimens
– Wildlife smuggling is very profitable
• Leopard fur / Rhinoceros horns
– U.S. Annual pet trade in wild species:
• 2 million reptiles
• 1 million amphibians and mammals
• 500,000 birds
• 128,000,000 tropical fish
– Cyanide released in coral reefs
Human-caused reductions in biodiversity
• Predator and pest control
– Many animal populations have been greatly reduced or exterminated
because they are regarded as dangerous to humans or livestock
– Animal control costs $20 million in federal and state funds annually
• 700,000 birds and mammals annually
– 100,000 coyotes
Endangered species management
• Hunting and Fishing Laws
– By 1890’s, most states had enacted some hunting and fishing laws
• General idea was pragmatic, not aesthetic or moral preservation
• In general, regulations have been extremely successful
Endangered Species Act
• Established in 1973
– Endangered are those considered in imminent danger of extinction
– Threatened are those likely to become endangered, at least locally, in the
near future
• Vulnerable are those that are naturally rare or have been locally
depleted to a level that puts them at risk
Endangered Species Act
• ESA regulates a wide range of activities involving endangered species:
– Taking (harassing, harming, pursuing, hunting, shooting, killing, capturing,
or collecting) either accidentally, or on purpose
– Selling
– Importing into or exporting out of the U.S.
– Possessing
– Transporting or Shipping
Endangered Species Act
• Currently, U.S. has 1,300 species on its Endangered and Threatened lists, and
about 250 candidate species waiting for consideration
– Number reflects more about human interests than actual status
• Invertebrates make up 75% of all species, but only 9% of T/E list
– Listing process is extremely slow
– Allocation of resources very uneven
Recovery plans
• Once a species is listed, USFWS is required to propose a recovery plan
detailing the rebuilding of the species to sustainable levels
– Total cost of all current plans = $5 billion
• Some have been very successful
– American alligator
– Bald eagle
• Many species have no recovery plan
Endangered Species Act
• Opponents have continually tried to require economic costs and benefits be
incorporated into planning
Reauthorizing ESA
• ESA officially expired in 1992
– Proposals for new ESA generally fall into two general categories:
• Versions that encourage ecosystem and habitat protection rather than
individual species
• Greater economic considerations
International Wildlife Treaties
• Convention on International Trade In Endangered Species (CITES) - 1975
– Regulates trade in living specimens and products derived from listed
species
Captive breeding
• Breeding programs in zoos and botanical gardens are one method of saving
threatened species
– Repositories of genetic diversity
• Most mammals in North American zoos are now produced from captivebreeding programs
– Many zoos now participate in reintroduction programs
Captive breeding
• Zoos have limited space for captive breeding
– How many can/should we save ?
– Ultimate problem is that natural habitat may disappear while we are
conserving the species itself
• Another alternative is to attempt to save species in the wild
– Provide funding for protection in native habitats