Conservation Biology

Learing goals:

* Know the potential benefits biodiversity confers to humans (ecosystem services)

* Be able to describe the major contributors to biodiversity loss

Conservation biology is an integrative discipline that applies the principles of ecology to evaluating the loss, maintenance, and restoration of of biodiversity

Realization of the rapid decline in diversity gave rise to the discipline in the 1980’s

Rationales for preserving species:
Ecosystem services (natural processes that support human activities):
 * water purification and enhancement of storage (i.e. percolation into soils),
* biomass for livestock forage, wood, and possibly energy (biofuels)
* healthy soils- lowers erosion
* pollination of crops
* pollution abatement- prevention of the spread of toxins into soils and surface waters (streams, rivers)
* CO2 uptake
Aesthetic value- recreational resource, religious value; Is this value greater than the economic gain associated with the loss of biodiversity?

There are approximately 10 million species, with more being described each year
Currently more than 16,000 species world wide are threatened with extinction due to various activities of humans
Mass extinction events are not unprecedented e.g. 65 million years ago (Cretaceous–Tertiary extinction event), dominant organisms on Earth went extinct in a very short period of time, possibly related to a catastrophic meteor impact that altered Earth’s climate; Other extinction events have occurred throughout Earth’s history; although the causes are uncertain, there has never been one like the present extinction event associated with a biological cause (anthropogenic)
Extinction rates are now 100 to 1000 times greater than the background extinction rates

Causes for higher extinction rates:

Habitat loss-
Associated with conversion of land for agriculture, domestic grazing, road construction, urban/ suburban development
Includes:
Habitat degradation - changes that reduce quality of the habitat for many, but not all, species.
Habitat fragmentation - breaking up of continuous habitat into habitat patches amid a human-dominated landscape.
Habitat loss - conversion of an ecosystem to another use.
> 80% of Earth has been modified -Most heavily impacted biomes are grasslands, deciduous forests, and tropical seasonal forests, but the rate of loss of tropical forests is greatest; 6 to 7 million hectares (23-27,000 square miles) are cut each year

Invasive species = non-native, introduced species
specialist native species are more threatened than generalist species by the effects of invasives
Approximately 20% of endangered vertebrates threatened due to invasives; higher rate on islands
Includes predators, herbivores, plants, pathogens
Control of invasive plants- Use of herbivores as biocontrol agents; Specialist herbivores can be used to control spread of invasive (non-native) plant species
General requirements:
* herbivore (usually insects) must be truly specialists & not attack native species
* must be effective- increase mortality and/or decrease recruitment
* have no other environmental effects (e.g. influence on predators) 

Overexploitation –
e.g. hunting, fishing, wood cutting

Pollution
emissions of industrial wastes, overapplication of fertizers, pesticides and herbicides, ozone, acid rain…
Cause direct toxicity to organisms, alters growth, and changes community composition (e.g. N deposition can favor invasive species)
One group of pollutants found in trace amount, but having a large impact are endocrine disrupting chemicals- similar in structure to hormones, or they block the production of hormones.  Can cause a change in the gender of the organism

Climate Change
to date only a few species have been endangered, but will worsen impact of habitat change, as organisms will be forced to migrate in order to track their “climate envelope,” increasingly encountering human development

How does extinction happen?
For some species, gradually, population by population; as populatios shrink in size, they become more susceptible to extinction (enter the “extinction vortex”)
Other species go quickly
Some species thought to be extinct are sometimes “rediscovered,” prompting increased efforts to conserve them

Loss of biodiversity includes dilution of native genes-  non-native species may be closely enough related to native species to hybridize with them
Great concern for the loss of genetic diversity in agricultural plants.  Domestication and breeding has led to genetically iniform plants, unable to adapt to changing environment or new pathogens