Threats to Biodiversity

Soule 2004 - traditional viewpoint of conservation

“Extinction is the most irreversible of all environmental calamities. With each plant & animal species that disappears, a precious part of creation is callously erased”

Modern view point of conservation

extinction, endangerment, and ecosystem are not the aims of human societies – they are an unfortunate byproduct of human activities (collateral damage)

What do we define as a threat?

There is no strict consensus, however, on what a threat is; sometimes hard to tell if an individual effect translates to a population level effect

Need to measure/quantify impacts

Threats to individuals may not threaten populations or species:

traditionally we call this a welfare issue not a conservation issue

the major threats to biodiversity HICOP

Habitat loss (land clearing, modification, fragmentation)

• number one leading threat

Invasive species (disease, predation, competition)

Climate change (weather, sea level rise, acidification)

• so far in terms of extinctions the least threatening but likely to rise

Overexploitation (overharvesting, overhunting, overfishing, poaching)

Pollution (burning of fossil fuels, dumping)

Habitat loss

no longer usable by biodiversity

Habitat degradation

more dangerous or difficult for organisms to live in. Caused by industry, agriculture, forestry, aquaculture, fishing, mining, sediment and groundwater extraction, infrastructure development, etc

Habitat fragmentation

reduces population viability

Invasive species

Introduction and successful colonization of species into places where they do not naturally occur

They can compromise native species through direct or indirect interactions

Invasive species - direct interactions

predation, competition, parasitism, disease, hybridization, toxins

Invasive species - indirect interactions

modifying habitats, disrupting species interactions, changing the relative densities of predators and prey

Climate change

• caused major extinctions before (geological record)

• global heating effects

• extreme weather events

• sea level rise

overexploitation

• exploitation, hunting, fishing (legal)

• Overexploitation, overharvesting, overfishing, overhunting, poaching (illegal)

• Main uses: food, traditional medicine, pet trade, apparel

• is now the #1 threat to many animal species

pollution

• dumping of chemicals and plastics into the environment

• burning of fossil fuels; circulation of chemicals atmospherically

• can affect animal endocrine systems and other aspects of animal health

• bioaccumulation

bioaccumulation

magnification of substances as you move up trophic levels

Multiple effects

many species, communities and ecosystems are under multiple threats (e.g., climate warming causing malaria to become an invasive species in northern Australia)

Synergistic effects

• total impact of two or more threats = more than the sum of those independent impacts

• Example: climate warming (coral bleaching) and fungal pathogens in corals

Global extinction

loss of a species from earth

Extirpation

loss of a species from one area/region

Functional extinction

reduced to such low densities that the species is likely to be unable to maintain populations (without intervention)

Ecological extinction

species reduced to such low densities that it is no longer relevant to other species or the community/ecosystem

Gopher tortoise – a keystone species

Gopher tortoises may be functionally & ecologically extinct in Louisiana

The Megafaunal extinctions

• Humans contributed to historical extinctions, for example the megafauna extinctions

• 70-90% of genera of megafauna (>44 kg in size) went extinct during the last ice age (Pleistocene, 44,000-72,000 years ago in Australia, 10,000-15,000 years ago in North America)

• These extinctions coincided with the arrival of humans in each area

• Which was responsible, climate change or human hunting?

Pacific Island bird extinctions

• 1,000-3,000 years ago

• Occurred as humans colonized the islands

• >2,000 species (particularly flightless rails) driven extinct by overexploitation, habitat loss, the introduction of rats, pigs and other animals carried by the Polynesians

• In some cases species went extinct within 100 years of human colonization

• There were patterns in these extinctions

Loss of a of a critical species such as a top predator can lead to a

trophic cascade, whereby the prey of those predators increases, and their prey decrease, etc

Trophic cascade

whereby the prey of those predators increases, and their prey decrease, etc

Mesopredator (ecological) release

increase in subordinate predators in response to the loss of top predators

Keystone species

greater impact on other species in the community than would be expected based on its numbers or biomass (e.g., pollinators, large predators)

Dominant species

common and have a strong effect on other species in the community (e.g., corals, trees, large herbivores)

Ecosystem engineer

so strongly modify habitat that their loss affects other members of the community (e.g., beavers, elephants, gopher tortoises)

Which species/groups are most at risk?

China has the reputation of fueling extreme overharvest, due to the importance of traditional medicine, heavy involvement in the pet trade, and dependence on wild species for protein

Traditional medicine

• The crocodile lizard is an endangered species

• It is believed to have medicinal value for curing insomnia due to its ability to sit still for long periods of time

IUNC Red List

IUCN = International Union for Conservation of Nature

Systematic listing of threatened and endangered species to be used as a diagnostic tool to help establish extinction risk of all species

Categories: Extinct, Extinct in the wild, Critically Endangered, Endangered, Vulnerable, Near Threatened, Least Concern, Data Deficient, Not Evaluated

Criteria: declines, population size, extent of range

IUNC Red List Categories

Extinct, Extinct in the wild, Critically Endangered, Endangered, Vulnerable, Near Threatened, Least Concern, Data Deficient, Not Evaluated

IUNC Red List Criteria

declines, population size, extent of range