Climate Change and Biodiversity: Extinction, Adaptation, and Mitigation

Extinction rate

Number of extinctions per year per species.

E/MSY

Extinctions per million species-years.

1 E/MSY

If there were 1 million species, about 1 extinction would be expected per year.

Background extinction rate

Based on the fossil record, about 1-2 E/MSY.

Sixth mass extinction

The current period of unusually high extinction associated with human activity, often called the Anthropocene.

Defaunation

The general decline in abundance of surviving animal populations, even when they have not gone extinct.

Greenhouse gases

Gases that trap heat in the atmosphere; this is a natural process necessary for life, but humans have increased their concentrations.

Current warming

Land and sea temperatures are about 0.9°C / 1.6°F warmer than pre-industrial levels.

Climate lag effect

Even if greenhouse gas concentrations stopped increasing immediately, additional warming would still occur because of the delay between emissions and heat trapping.

Climate change: melting ice

Sea ice, glaciers, and continental ice sheets are declining or melting.

Sea ice

Frozen ocean water; its volume and extent are declining.

Climate change: sea-level rise

Caused by melting glaciers/ice sheets and thermal expansion of warming seawater.

Observed sea-level rise

Sea level has risen approximately 21-24 cm since 1880.

Tidal Basin climate example

Sea-level rise threatens historic places such as the Tidal Basin in Washington, D.C.

Projected sea-level rise

Projected to rise at least about 1 meter over the next 100 years according to the notes.

U.S. coastal population example

About 52% of the U.S. population lives near the coast.

Climate change: extreme drought and rainfall

Precipitation has increased in the eastern U.S. and decreased in the west; long dry periods can harden soil.

Climate change: stronger storms

A warmer atmosphere contains more energy that can contribute to stronger storms.

Ocean acidification

Increased absorption of atmospheric CO2 lowers ocean pH and makes oceans more acidic.

Positive feedback loop

A change that produces additional changes that reinforce and amplify the original change.

Melting ice positive feedback

Melting ice reduces reflective surfaces, allowing the Earth/ocean to absorb more heat, producing more warming and more melting.

Permafrost positive feedback

Melting permafrost releases stored greenhouse gases, increasing atmospheric greenhouse gases and causing additional warming and melting.

Fire positive feedback

Earlier snowmelt and longer summers increase fire size/frequency; fires release stored carbon, increasing greenhouse gases and further warming/drying.

Areas most vulnerable to climate change

Coastal areas, the Arctic and Antarctica, islands and low-lying areas, and drought- or flood-prone regions.

Climate-driven range shifts

Species may move poleward or upward in elevation to remain in cooler conditions.

Marine species and range shifts

Marine organisms may move poleward relatively easily.

Terrestrial range-shift examples

Birds, butterflies, reptiles, amphibians, and invertebrates may shift poleward or upward.

Ocean acidification and calcification

Marine organisms with calcium carbonate shells/skeletons may have reduced calcification or experience dissolution under acidic conditions.

Oxygen limitation hypothesis

Higher temperatures increase oxygen demand and heart rate while potentially reducing available blood oxygen, causing anaerobic metabolism and waste buildup.

Phenology

The timing of seasonal biological activities.

Phenology: small birds

Some small bird species are laying eggs earlier.

Phenology: migratory birds

Some migratory birds are changing migration timing or ceasing migration.

Phenology: plants

Some plant species are budding and flowering earlier in spring.

Behavioral adaptation to climate change

Changing behavior or activity timing to reduce exposure to increasing temperatures.

Nocturnal activity example

An organism may become more active at night to avoid daytime heat.

Genetic adaptations to climate change

Potential evolutionary changes include reduced body size or greater resistance to harmful anaerobic metabolic products.

Climate change and species interactions

Rising temperatures can alter interactions between species that previously depended on stable environmental cues.

Coral bleaching example

Rising temperatures can decouple the mutualistic relationship between coral and algae, producing coral bleaching.

Environmental cues and climate change

Species may rely on different environmental cues such as temperature, rainfall, light, or day length, causing mismatches as climate changes.

Great tit case study

Great tits time nesting so chicks hatch when caterpillars emerge, but caterpillar emergence depends on oak budding, creating the potential for climate-driven mismatch.

Great tit-oak-caterpillar cues

Oaks respond to rainfall/light, caterpillars respond to oak development, and great tits respond to caterpillar timing, so climate change can uncouple the system.

Climate-change extinction vulnerability

Species at poles, high elevations, and low-lying islands are especially vulnerable because they may have nowhere else to move.

Island species climate vulnerability

Many island species are endemic and cannot simply migrate elsewhere when sea-level rise causes habitat loss.

Community response to climate change

Biological communities do not move or respond as a single unit; individual species respond at different rates and in different directions.

Future ecosystems

Current communities may disassemble and surviving species may form new ecosystem combinations that are difficult to predict.

Emission reduction

New technologies, reduced fossil-fuel reliance, and renewable energy can reduce greenhouse gas emissions.

Reforestation potential

About 1 billion hectares outside urban/agricultural areas could potentially be converted to forest and store approximately 205 gigatons of carbon.

Reforestation atmospheric CO2 estimate

The notes state that large-scale reforestation could absorb about 25% of current atmospheric CO2.

Agricultural emission reduction

Reducing large-scale agricultural emissions, including methane from cattle, can help mitigate climate change.

Land and water protection for climate adaptation

Increase protected areas and protect or restore core habitat of threatened species.

Population size and climate resilience

Larger populations contain more potential for adaptation and therefore greater resilience to climate change.

Problem with static reserve networks

Protected areas fixed in one location may fail to meet their original conservation objectives as species ranges shift.

Climate-smart reserve design

Create reserves across elevation gradients and protect movement corridors, stepping stones, and refugia.

Refugia

Areas expected to experience relatively minimal climate impacts and therefore provide shelter for species.

Bird island example

Dredged sediment can be used to create artificial "bird islands" that may offset climate-driven habitat loss along the Atlantic Coast.

Assisted migration

Translocating species threatened by climate change to areas where they may be able to survive.

Risk of assisted migration

The best future locations are difficult to predict, and translocated species could cause negative effects or become invasive.

Captive populations

Establishing captive populations can prevent extinction when survival in the wild is unlikely.

Reduce non-climate pressures

Reducing other threats can increase species' ability to adapt and evolve in response to climate change.

Australia mammal extinction case

Australia is described in the notes as a world leader in mammal extinctions, with 38 since European settlement in 1788.

Australian mammal extinction significance

About one-third of global mammal extinctions over the past 500 years occurred in Australia according to the notes.

Australian extinction rate

Approximately 1-2 mammal extinctions per decade according to the notes.

Critical weight range

Australian mammals between about 35 g and 5.5 kg have been particularly vulnerable.

Australian savior populations

Many threatened mammals survive mainly on islands or within intensively managed fenced areas.

Cats and foxes in Australia

Introduced cats and foxes are major contributors to Australian mammal declines.

Domestic cat

A cat kept and cared for by humans.

Stray cat

A lost, abandoned, or escaped domestic cat.

Feral cat

A free-living wild cat.

Australian feral cat abundance

The notes estimate about 2.8 million feral cats.

Annual prey consumption by one feral cat

Approximately 393 mammals, 225 reptiles, 129 birds, and 44 frogs per year according to the notes.

Daily Australian cat predation

The notes state cats kill about 3.2 million mammals, 1.9 million reptiles, 1.2 million birds, and 250,000 frogs per day in Australia.

Invasive species

A species that arrives, often with human assistance, in a habitat it did not previously occupy, establishes a population, and spreads autonomously.

Non-native vs invasive

Not all non-native species are invasive.

Non-native crop example

Many crop and ornamental garden species are non-native but not invasive.

Invasive species from same country example

Lake trout introduced into Yellowstone from the Great Lakes demonstrate that an invasive species does not have to come from another country.

Pest

A species that causes environmental, economic, or human-health problems.

Pest vs invasive

Not all invasive species are pests and not all pests are invasive species.

Deliberate introduction

Human intentional introduction of a species into a new environment.

Acclimation societies

Colonial-era organizations that intentionally introduced familiar European plants and animals for aesthetic, economic, or nostalgic reasons.

Pet-to-pest pipeline

Exotic pets escape or are released and establish invasive populations.

Florida iguana example

Exotic pet iguanas have become invasive in Florida.

Biological control

Deliberate introduction of a natural enemy such as a predator, parasite, or pathogen to control another species.

Cane toad case study

Cane toads were introduced to Australia in 1935 to control sugar-cane beetles.

Initial cane toad introduction

About 100 cane toads were imported in June 1935.

Cane toad abundance

More than 200 million were estimated by 2011.

Cane toad invasion speed

The invasion front has moved at approximately 60 km per year.

Cane toad effectiveness

The notes state there is no evidence they significantly reduced cane beetle numbers.

Horticulture introduction

Plants introduced intentionally for landscaping can later become invasive.

Chinese privet example

Chinese privet was introduced as an attractive hedge but can choke riverbanks.

Accidental introduction

An organism is unintentionally transported into a new environment.

Cargo-ship hitchhikers

Rats and cats may escape from cargo ships onto predator-free islands and cause catastrophic declines.

Ballast water

Water carried by ships for stability that can transport aquatic invasive organisms between regions.

Northern Pacific sea star example

Transported through ballast water and listed among major invasive alien species.

Enemy release hypothesis

Introduced species may thrive because they leave behind predators and parasites from their native range.

Feral cats and enemy release

Feral cats have relatively few predators in Australia, although wedge-tailed eagles occasionally prey on them.

Prey naïveté

The failure of prey to appropriately recognize or respond to a novel predator.

Prey naïveté type 1

Prey fail to recognize the threat and show no antipredator response.

Prey naïveté type 2

Prey recognize the predator but respond inappropriately.

Prey naïveté type 3

Prey produce an appropriate response, but the response is ineffective.

Invasion lag time

A period of slow population growth/spread after introduction followed by rapid population increase and expansion.