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The nonnative legume Albizzia procera was used to add organic material to nitrogen-depleted soils in Puerto Rico,
enabling indigenous plants to recolonize the area and overgrow the introduced plant.
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Benefits of biodiversity include:
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Biodiversity can be measured at three levels:
| Detail of animals in a Paleolithic mural, Lascaux, France | Biologist Carlos Rivera Gonzales examining a tiny tree frog in Peru |
| Harvard biologist E. O. Wilson believes that humans have evolved an innate affinity for natural environments rich in biodiversity - biophilia. | |
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An artificial corridor.
This bridge in Banff National Park, Canada, helps animals cross a human–created barrier.
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Species such as ruffed grouse
and white–tailed deer thrive in ecotones, but artificial edges can fragment natural habitats.
As forests become fragmented, edge-adapted species such as the Brown–headed Cowbird
benefits at the expense of songbirds that require large, intact forests for nesting.
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Amazon rain forest fragments; small fragments favor edge-adapted species.
Fragmented
habitats can be connected by a movement corridor
to facilitate gene
flow between populations, but this can also serve as a vector for the spread of disease and alien species.
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The polymerase chain reaction (PCR) uses DNA polymerase
extracted from thermophilic prokaryotes (Archaea) from hot springs and hydrothermal vents.
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Ecotones such as estuaries and wetlands exhibit high productivity and diversity.
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The low elevation and abundant vegetation in wetlands serve to collect excess rain water and control floods.
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Habitat fragmentation in the Mount Hood National Forest.
Many species cannot survive on small fragments of habitat.
A male black bear needs a territory of about 70 sq. km, whereas gray wolf packs need at least 100 sq. km.
Populations confined to small habitats also suffer loss of genetic diversity due to genetic
drift.
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Amazon rain forest fragments, isolated sections of forest ranging in area from 1 to 100 ha.
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Long-term monitoring of a grizzly bear population.
Studies by John and Frank Craighead, shown here placing a radio collar on a tranquilized grizzly bear,
resulted in population estimates that were essential to Mark Shaffer's population viability analyses.
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Growth of the Yellowstone grizzly bear population,
as indicated by the number of females observed with cubs and the number of cubs.
The effective population size (Ne) is based on the breeding potential of a population, incorporating information about the sex ratio of breeding individuals.
Ne = 4NfNm / (Nf + Nm)Nf and Nm are the numbers of females and males that successfully breed.
Ne is also affected bylife history traits such as family size, maturation age, genetic relatedness among population members, gene flow, and population fluctuations.
Shaffer estimated that a total grizzly bear population of 70 to 90 individuals would have a 95% chance of surviving
for 100 years.
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A hundred heartbeats from extinction.
Three members of what Harvard biologist E. O. Wilson
calls the Hundred Heartbeat Club,
species with fewer than 100 individuals remaining on Earth.
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Earth's terrestrial biodiversity hot spots.
A biodiversity hot spot is a relatively small area with an exceptional concentration of
endemic species and a large number of endangered and threatened species;
usually there is a bias toward vertebrates and plants.
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Disruption of interaction networks.
The endangered Marianas “flying fox” bat (Pteropus mariannus) is an important pollinator and seed
disperser for over 79% of the trees on the Samoan islands, but is being
hunted as luxury food items.
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Introduced species.
The brown tree snake has exterminated 12 species of birds and 6 species of lizards on Guam
since WW II.
The kudzu was introduced to control soil erosion and has smothered native vegetation in the
southern US.
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Overexploitation.
North Atlantic bluefin
tuna are auctioned in a Japanese fish market.
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The rosy periwinkle (Catharanthus roseus), a plant that saves lives.
This Madagascar plant contains alkaloids that inhibit cancer cell growth in Hodgkin's disease and childhood leukemia.
25% of all prescriptions dispensed from pharmacies contain substances originally derived from plants.
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What caused the drastic decline of the Illinois greater prairie chicken population?
EXPERIMENT Researchers observed that the population collapse of the greater prairie chicken was mirrored in a reduction in fertility , as measured by the hatching rate of eggs. In 1992, researchers began experimental translocations of prairie chickens from Minnesota, Kansas, and Nebraska in an attempt to increase genetic variation.
RESULTS After translocation (blue arrow), the hatching rate rapidly improved, and the population rebounded.
CONCLUSION
The researchers concluded that lack of genetic variation had started the Jasper County population of prairie
chickens down the extinction vortex.
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Habitat requirements of the red–cockaded woodpecker.
Red-cockaded woodpeckers drill nest holes in mature longleaf pine trees which have begun to decay from fungal
infections. They also require forests with low undergrowth for social interactions.
Habitat deterioration due to logging and fire suppression led to the decline of this species.
Supporting viable populations required protection of pine forests with use of controlled fires,
and constructing breeding cavities.
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Tropical dry forest, Costa Rica.
Clearing for agriculture, mainly for livestock grazing, eliminated about 94% of tropical dry forest in Central America and Mexico.
In a reversal of roles,
tropical dry forest restoration has used domestic livestock
to disperse the seeds of native trees into open grasslands.
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Rhine River, Europe.
Centuries of developing and channeling for navigation have straightened the once-meandering Rhine River and disconnected it from its floodplain and associated wetlands.
France, Germany, Luxembourg, the Netherlands, and Switzerland are cooperating to reconnect
the river to side channels, which increase the diversity of habitats available to aquatic biota, improve water quality,
and provide flood protection.
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Kissimmee River, Florida.
The Kissimmee River was channelized from a meandering river into a 90-km canal, with significant negative impacts on fish and wetland bird populations.
Kissimmee River restoration has filled 12 km of drainage canal and reestablished 24 km of the original 167 km of
natural river channel.
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Coastal Japan.
Seaweed and seagrass beds are important nursing grounds for a wide variety of fishes and shellfish.
Once extensive but now reduced by development, these beds are being restored in the coastal areas of Japan.
Techniques include construction of suitable seafloor habitat,
transplanting from natural beds using artificial substrates,
and hand seeding.
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Truckee River, Nevada.
Damming and water diversions reduced flow in the Truckee River, leading to declines in riparian forests.
Restoration ecologists worked with water managers to allow water to be released during the short season of seed release by native cottonwood and willow trees for seedlings to become established.
This controlled-flow release led to a dramatic recovery of cottonwood-willow riparian forests.
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Succulent Karoo, South Africa.
In this desert region, overgrazing by livestock has degraded vast areas.
Reversing this trend, private landowners and government agencies are restoring large areas of this unique region.
The photo shows a small sample of the exceptional plant diversity of the Succulent Karoo;
its 5,000 plant species include the highest diversity of succulent plants in the world, such as the rare
Aloe pillansii.
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The size-time relationship for community recovery from natural and human-caused disasters.
Note that the scales are logarithmic.
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Infant mortality and life expectancy at birth in Costa Rica.
The success of conservation programs such as zoned reserves and ecotourism in Costa Rica
is a model for sustainable development to improve living standards for humans while conserving biodiversity.
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Genetic drift
can push species such as the Greater Prairie Chicken
down an extinction vortex.
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The legal (green border) and biotic (red borders) boundaries
for grizzly bears in Yellowstone and Grand Teton National Parks.
The biotic boundaries are defined by the entire watershed for this region and the area necessary to support a minimum viable population (MVP) of grizzly bears.
America's first National Park was established in 1872.
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Zoned reserves in Costa Rica.
Costa Rica has eight zoned reserves, called “conservation areas,” which contain national park land.
The buffer zones provide a steady, lasting supply of forest products, water, and hydroelectric power, as well as support sustainable agriculture and income from ecotourism.
This can be a model for sustainable development.