Conservation Biology

•Applied scientific discipline that seeks to counter the current rapid decrease in the diversity of life on Earth – biodiversity

•Human population size, and per capita rates of resource use in particular, are regarded as the “ultimate” (root, in this sense) cause of the “Biodiversity Crisis”

•Components of biodiversity…what is it we’re trying to save?

•genetic diversity, species diversity, ecosystem diversity…

•integrity of ecological and evolutionary processes; ecosystem functions and processes

Raven and Johnson 1999

Population growth is highest in tropical and subtropical countries. Mexico City, the world’s largest city, has well over 20 million inhabitants

A global perspective on the biodiversity crisis

•~1.5 million species described; estimates of total species diversity; 10 to 30-80 million species

•Many, perhaps up to half, of Earth’s species live in tropical forest biome, which is being logged and converted to cropland at a very high rate

•Globally the amount of human-altered land surface is near 50%; we use over 50% of all accessible surface fresh water

•Rates of diversity loss and ecosystem degradation may now exceed the K-T asteroid

•Human activities are altering ecosystem processes on a global scale

Deforestation rates are high in tropical forests. Central America is a good example of the high rate of destruction of tropical forest As the forests are lost, so are the many species that live in them

HUMAN POPULATION(Size and Resource Use)

CO2 INCREASE

ALTERED BIOGEOCHEMICAL CYCLES

PERSISTENT ORGANIC COMPOUNDS

LAND USE AND LAND COVER CHANGE

HARVESTING NATURAL POPULATIONS

BIOLOGICAL INVASIONS

GLOBAL CLIMATE CHANGE

LOSS OF BIOLOGICAL DIVERSITY

Viitousek et al 1997

human-caused global changesCO2 INCREASE

ALTERED BIOGEOCHEMICAL CYCLES

PERSISTENT ORGANIC COMPOUNDS

LAND USE AND LAND COVER CHANGE

HARVESTING NATURAL POPULATIONS

BIOLOGICAL INVASIONS

proximate causes of changes(forestry, grazing, ag-related commerce)

INDUSTRY AGRICULTURE

Greatest threat to biodiversity globally are related to habitat loss and degradation

The three principal forms of habitat loss and degradation are:

•habitat destruction

•habitat alteration

•habitat fragmentation

•Fragmentation is often a consequence of human land conversion activity; the remaining patches are surrounded by areas variously altered by humans

•Fragmentation has become a major subject of research in conservation biology

Habitat fragmentation break up of extensive tracts of habitat into small, isolated patches. Aerial photo of Mt. Hood National Forest in the western U.S. shows common result of ecosystem alteration; “islands” of coniferous forest remain following logging

Biodiversity problems in the U.S.

Proportion of U.S. Species extinct or at risk. The groups that are most endangered – mussels, crayfishes, amphibians and fishes – live in freshwater, a habitat that has been extensively destroyed and polluted

Habitat destruction and degradation is the primary cause of extinction and endangerment for freshwater aquatic organisms

Small animals are vulnerable to habitat destruction because they often have small ranges and highly specialized requirements

WHY SHOULD WE ATTEMPT TO CONSERVE BIODIVERSITY?

•Conservation biology is driven by the value of biodiversity

•instrumental values

•support anthropocentric, utilitarian rationales that hold that biodiversity has value as a means to human ends

•instrumental values include

•goods (actual and potential food, medicine, fiber, fuel)

•services (pollination, nutrient recycling, oxygen production

•information (practical scientific knowledge, genetic library)

•psycho-spiritual satisfaction (natural beauty, religious awe, pure scientific knowledge)

•intrinsic values

•Support biocentric rationales that hold that biodiversity has value simply because it exists

•The “Conservation Movement” was born in the U.S., first half of the 20th Century; its roots can be traced back to philosophical movements of the 19th and 20 centuries

•Romantic-Transcendental Conservation Ethic

•derived from writings of Thoreau, Emerson (east) and Muir (west)

•first prominent writers to argue in the mid 1800’s that nature has uses other than economic gain; spoke of nature in a quasi-religious sense

•Resource Conservation Ethic

•rooted in the utilitarian philosophy of John Stuart Mill

•popularized by forester Gifford Pinchot, late 19th early 20th century

•stressed equity of resource use amongst consumers; formed basis of the multiple-use concept of USFS and BLM

Cultural and Scientific History of Conservation of Biodiversity

Preservationist movement, advocating pure wilderness and a spiritual appreciation for nature

Conservation movement, advocating a resource-based, utilitarian view of the world

Meffe et al 1997

http://sierraclub.org/john_muir_exhibit/index.html

John Muir Gifford Pinchot

•The modern conservation movement was born in the 20th century, emerging with the development of evolutionary ecology

•Evolutionary-Ecological Land Ethic

•Developed by Aldo Leopold in his classic essays in A Sand County Almanac (1949) and other writings

•Leopold saw ecosystems in the context of integrated systems and interdependent processes and components – an equilibrium perspective

•Leopold’s equilibrium perspective has since been replaced by a dynamic, nonequilibrium perspective

•Nevertheless, the Leopold land ethic, rooted in principles of ecology and evolution, remains as the philosophical foundation for conservation biology

It is inconceivable to me that an ethical relation to land can exist without love, respect, and admiration for land, and a high regard for its value. By value, I of course mean something far broader than mere economic value; I mean value in the philosophical sense.

Aldo Leopold 1949

Aldo Leopold

photo: http://www.naturenet.com/alnc/aldo.html

Frances and Frederick Hamerstrom

Cultural and Scientific History of Conservation of Biodiversity

Changes in wooded area of Cadiz Township, Green County,Wisconsin,during the period of European settlement. Shaded areas represent the amount of land in forest in each year

(Maffee et al 1997)

Fragmentation and Metapopulations

•One common consequence of fragmentation is the subdivision of a formerly continuously distributed populations into a metapopulation

•Typically, subpopulations exist in patches of varying size and quality

•Larger patches with abundant, high-quality resources tend to have more persistent subpopulations – higher reproduction and lower mortality rates – that subpopulations in smaller patches with poorer, fewer resources

Sources and Sinks

•Persistent subpopulations may be a source of new individuals that disperse to other patches

•Source habitat = area where reproduction exceeds mortality and from where individuals disperse

•Subpopulations in small, poor patches may persist in low numbers or be extinction prone – sinks where dispersers either join the existing population or recolonize the patch

•Sink habitat=area where mortality exceeds reproduction

Florida Scrub Jays are cooperative breeder, and an endangered species with a metapopulation distribution

High quality oak scrub habitatat Low quality oak scrub habitatat

•Population Modeling: Survival probabilities of FSJ populations

“Monte Carlo” simulation techniques: natural birth and death processes are allowed to proceed each year indefinitely, until the number of breeders is reduced to one or zero (population extinct)

This is a stochastic, not deterministic, approach to modeling (simulating) behavior of populations

Repeat process for populations of different initial sizes

•The process is repeated 100 times, generating a frequency distribution of years-to-extinction

•Assumptions include:

•each territory contains one pair of breeding jays

•popul. is at carrying capacity to start with – can not exceed initial size

•helpers per territory vary between 0-3

•yearlings don’t breed

Demographic (life history) values and their annual variations used in computer simulation of Florida Scrub Jay populations

Cumulative extinction probabilities versus time for Florida Scrub Jay populations of different maximum sizes measured in no. of territories. Epidemic occur at random intervals with a mean frequency of one every twenty years

Same methods, but epidemic occur at random intervals with a mean frequency of of one every fifty years. Dashed lines show analogous extinction curves for FSJ pops. fragmented into 2,3 or 4 isolated populations of 5 territories each