Extinction of Species

what is the primary unit of biological diversity in this class?

species

Why protect biodiversity?

utilitarian values and intrinsic values

what is the difference between the projected future extinction rate and the current rate

future is ten times higher

what is the difference between the current extinction rate and the fossil record

the current is 1000x higher

what is driving the current extinction trend?

human population growth and consumption crisis

what are the major threats to species?

• habitat loss

• climate change

• disease

• invasive species

• over-exploitation

• pollution

describe conservation biology as a discipline

crisis-oriented and mission-driven

what are the assumptions of conservation biology?

• diversity of species should be preserved and has intrinsic value

• untimely extinction of species should be prevented

• ecological complexity is good

• evolution is good

how has conservation biology made a difference?

• loss of biodiversity is now an increasingly acknowledged issue

• conservation biology is a recognized and respected field

• maintaining biodiversity is now an over-arching theme for natural resource managers

what is biological diversity?

• genetic diversity among individuals within a species

• the complete range of species in a given area

• how species interact within an ecosystem

gene

a segment of DNA whose nucleotide sequence codes for a protein

allele

alternative form of a gene

when is genetic diversity high within a species

heterozygosity is high

genotype

alleles present at a given gene

phenotype

physical characteristics of an individual determined by its genotype

why is genetic diversity important for species long term?

genetic diversity increases phenotypic variation and thus the ability of species to adapt to future environmental change

why is genetic diversity important for species short term

loss of genetic diversity increases the risk of extinction through inbreeding depression and compromised disease resistance

species diversity

variety of species in a given area

primary objective of modern conservation biology

maintaining species diversity by preventing the extinction of individual species

morphological species

group of individuals that is morphologically, physiologically, or biochemically distinct from other species

who commonly uses the morphological species definition

taxonomists

what are the problems with the morphological species definition

• individuals of a single species can look very different yet interbreed

• morphology can vary in wild species as well

• morphologically similar species diverged millions of years ago and are not capable of interbreeding

biological species definition

a group of individuals that actually interbreed or can potentially interbreed in nature, not necessarily grouped according to similarity of appearance

which species definition is the most common for living mammals, birds, and fish

biological

problems with BSD

• interbreeding occurs pretty commonly (hybridization)

evolutionary species definition

group of individuals that is evolving together and separately from other groups

problems with the evolutionary species concept

strictly evolutionary classifications can be counterintuitive

what is the most common definition in conservation purposes

BSD

ecosystem

biological community of species interacting with each other and with the physical and chemical environment

ecosystem services

range of benefits provided to people from ecosystems

extinct

no member of the species remains alive anywhere in the world

extinct in the wild

only alive in captivity

locally extinct/extirpated

no longer found in an area it used to inhabit but is still found elsewhere

ecologically extinct

persists in such low numbers that its effects on other species is insignificant

normal background extinction rate

1-10 species out of 10 million

mass extinction

elevated extinction rates that lead to a sharp decrease in the number of species in a “short” time span

what are possible causes for mass extincitons

• asteroids

• global volcanic activity

• ocean anoixa

• climate change

how do extinction rates during the past 500 years compare to those during mass extinction events?

much greater

how do extinction magnitudes compare to those during several mass extinctions?

much smaller

what does the global distribution of animal extinctions suggest?

biases in documentation

how did the emergence of tool-making change evolution?

it created an unequal playing field and we became the hunters

what are the big trends in the current mass extinction?

• “recent” over-exploitation, habitat loss, and introductions of invasive species are currently the biggest drivers

• climate change, pollution and disease are major emerging threats

• species are threatened in increasingly complex ways

where are endangered species concentrated?

the developing world

what are the two types of values?

utilitarian and intrinsic values

utilitarian values

make a species worthwhile as a means to help human beings achieve their ends

intrinsic values

makes a species worthwhile in its own right as an end in itself

goods

species recognized as tangible resources that human beings consume

services

species that perform useful functions that benefit human beings

information

species that help human beings gain insights and knowledge

inspiration

species that evoke wonder, awe and love from human beings

what are examples of utilitarian values

goods, services, information, inspiration

describe wild species as goods

• only a small proportion

• value of those species can be quantified and monetized

describe wild species as services

• less obvious to most people

• includes decomposition, plant pollination, nitrogen fixation, pest control

• although provided without cost, we know they are valuable, and they can be quantified and monetized

• over $33 trillion per year

describe wild species as sources of information

• many discoveries that will improve human lives will come from studies of wild species

• Darwin noted “the loss of species uncared for and unknown is like burning books no one has read”

• biotechnology depends on genetic information stored in wild species

describe wild species as inspiration

• our attraction to wild species may be in our genes according to the “biophilia” hypothesis

• we use wild species as potent symbols

• but our affections are limited to species with certain traits, especially those of the “charismatic mega-vertebates”

• difficult to quantify or monetize

• conservationists use these values strategically

what are the options for quantifying and monetizing these utilitarian values?

commodity, option, contingent, existence, and bequest values

commodity values

what people are willing to pay when there is a market for the species

option values

what people are willing to pay to guarantee option of finding future use for a species

contingent values

what people would be willing to pay for the opportunity to use a species

existence values

what people are willing to pay to keep a species from going extinct, even if they never actually use it

bequest values

what people are willing to pay to assure future generations have opportunity to use a species

describe the value of coral reefs

• goods totaled $3008 per hectare

• services totaled $2805 per hectare

• inspiration totaled $1 per hectare

• total for 8 values was $6075 per hectare

• for the world’s 62 million hectares of coral reef, the overall value is $375 billion per year

what type of value has been a winning argument for conservation of wild species

utilitarian

what are the difficulties applying utilitarian values to all wild species

• ignorance of wild species is a major obstacle

• irreversibility of extinction argues for a precautionary approach that is difficult to defend economically

• interdependence of species could result in the extinction of a ‘worthless’ species affecting a valuable resource

why is bestowing intrinsic value on wild species so controversial?

• philosophers typically limit intrinsic value and the right to exist to rational human individuals who have their own independent goals, but not usually to groups or to non-human individuals

• perhaps individual organisms also have intrinsic value because each individual has common goals (to grow, survive and reproduce) that are independent of the goals of human beings

• maybe the idea of “animal rights” fits, but what about a species? Does a species have intrinsic value?

safe minimum standard

assumes that biological diversity is of incalculable value and should always be conserved unless the costs of doing so are intolerably high

what are the different ethical dimensions?

anthropocentric, stewardship, biocentric, and ecocentric

anthropocentric ethic

• only human beings are worthy of ethical treatment

• only human well-being matters as a basis for deciding what’s right or wrong

• it’s only unethical to cause extinction if the loss of the species negatively impacts human beings

• can actually be used to argue for species preservation

stewardship ethic

• often has a religious basis

• human beings, as the highest form of life, have responsibilities to care for other species

• can lead to preservation of species as long as it doesn’t interfere with human goals, but human needs still come first because of our exalted position

biocentric ethic

• based on a reverence for life

• places individual human beings on an even par with individuals of other species

• has been the moral basis for the animal rights movement

• usually ambiguous on species and doesn’t necessarily regard causing extinction as unethical

ecocentric ethic

• has an ecological/evolutionary basis and focuses on the species rather than the individual

• homo sapiens is a coequal with other species

• human behavior should not threaten other species or disrupt ecological systems (unique)

• Aldo Leopold stated it as an ecocentric Golden Rule: “A thing is right when it tends to preserve the integrity, stability and beauty of the biotic community; it is wrong when it tends otherwise”

• many conservation biologists and environmentalists espouse this moral code of ethics

how many species have been identified?

around 1.5 million

what is the best estimate for species globally?

5-10 million

what are the high diversity ecosystems?

tropical rainforests, coral reefs, mediterranean-type communities

describe tropical rainforests

• only 7% of land area, but >50% of terrestrial species

• 5 million? insect species

• 40% of plant species

• 30% of birds

describe coral reefs

• produced by stony corals, colonial cnidarians that secrete an exoskeleton of calcium carbonate

• “rocky” formations from accumulation of skeletal material support living corals and high plant and animal diversity

describe mediterranean-type communities

• hot summers and wet winters

• high species diversity, particularly plants, fire

factors causing geographical differences in species diversity

biogeography, environmental gradients, disturbance regimes

describe environmental gradients

primary production, latitude, elevation, complexity

describe environmental gradient, productivity

• precipitation and year round warm temperatures increase primary production

• increases energy availability food for individual organisms and, ultimately, population sizes

• increases the ability of species to specialize

describe environmental gradient, latitude

general pattern or increasing diversity with decreasing latitude

describe disturbance regimes

• absence of disturbance can promote competitively dominant species

• frequent and severe disturbances can kill individuals and destroy habitat

• moderate levels of disturbance can result in higher species diversity due to “patchy” habitats

species richness

reflects the number of species in a community

alpha richness

the number of species within a local area, can be calculated as the average richness in local areas within a larger region

gamma richness

total number of species across a larger region

beta richness

change or turnover of species across a region beta= gamma/average alpha diversity in the region

what are biodiversity hot spots targeted based on?

species diversity, levels of threat, endemism

criticisms of the hotspot approach

• lack of concordance among taxa: protecting hotspots doesn’t necessarily conserve the full range of species diversity

• do not consider genetic diversity

• often do not consider difference in cost of land among hotspots

• do not consider ecosystem processes and services, only species diversity

what is the ability of species to survive environmental change dependent (in part) on?

ability to adapt

what happens to species that don’t adapt, move, or acclimatize?

go extinct

speciation

evolutionary process by which multiple new species arise from a single ancestral species

speciation rate

number of new species created per unit time

what depends on how populations evolve in response to changing environments

extinction and speciation

biological evolution

changes in inherited traits (that have genetic basis) over time

microevolution

changes in traits in a population from one generation to the next

macroevolution

creation of multiple species from a common ancestor over many generations

allopatric speciation

single population is split into two populations by geographic barrier that then evolve into separate species

peripatric speciation

new species are formed in small, isolated populations created by long-distance “dispersal”

parapatric speciation

between two groups of individuals occurring side by side when one is exposed to a new environment

sympatric speciation

occurs in the same location in the absence of a physical barrier via evolution of behavioral differences