Habitat Loss, Degradation, and Fragmentation

What are the causes of habitat loss/modification?

• over exploitation

• agricultural activity

• urban development

• invasion/disease

• resource extraction (ex. mining)

• pollution

• system modification (ex. fire, dams)

• climate change

What is the primary driver of habitat loss?

agricultural expansion

How does habitat loss reduce ecosystem services?

Can lose species providing coastal protection, carbon storage, water filtration, etc.

How can habitat loss/degradation shift communities?

• can decrease/increase populations of species

• migrants can increase

What are causes of habitat degradation?

• pollutants ie. pesticides, oil spills, heavy metals

• chemicals ie. hormones, detergents, antibiotics

• plastics

• eutrophication (algae turning water anoxic)

• acid rain

• desertification

• erosion

How does increased farmland affect native species?

overall decline in native species, but some species do better. downstream trophic affects must be considered

What can pollutants likes DDT result in for top predators?

Biomagnification/bioaccumuation in individuals at higher trophic levels

How are different biomes affected by habitat degredation?

• tropics and subtropics have much more annual forest loss

  • temperate forests are increasing

Why is habitat loss occurring at a higher rate for tropics/subtropics than temperate forests?

• tropic species aren’t as accustomed to high-distrubance events

• more removal of native land for agriculture than temperate forests

Why is habitat loss occurring at a lower rate for temperate forests than in the tropics/subtropics?

• species more accustomed to high-disturbances

  • humans leaving for urban centers

What are causes of habitat loss/degradation in coral reefs?

• destruction

• chemical pollution

• tourism

• sedimentation

• coral bleaching

How does the number of patches correlate to habitat amount?

• high and low habitat percents associated with few patches

• 50% habitat amount has more patches

How does patch size correlate to habitat amount?

• low habitat amount = small patches

• high habitat amount = large patches

How does patch isolation correlate to habitat amount?

• less habitat = more isolated, further from neighbors

  • more habitat amount = less isolated, closer to neighbors

How does the total edge amount of a patch correlate to habitat amount

• small and large habitat amount = little edge

• medium habitat amont = lots of edge (many intermediate patches)

What effects does a small patch size have on the species present?

• reduced immigration, higher extinction rates

• increased genetic drift

• increased species distinction over time

What happens to the edge of the habitat as the habitat size decreases?

the percent of the patch made of edge increases

What is the interior habitat of a patch affected by?

size and shape of patch

What are the effects of edge habitats?

• changes in microclimate ex. lack of foliage coverage

• less buffering of climatic variation ex. more exposure to sun, wind

• increased disturbance ex. human interactions, chemicals, pollutants

• increased susceptibility to invaders, pests, etc.

What are ecological traps and where do they often occur?

• when organisms are attracted to poor-quality habitats because of previously reliable cues misleading them. reduces their survival and reproduction (lowers fitness)

• ex. sea turtles following house lights

How has past natural selection in high-disturbance environments impacted the effects of fragmentation?

species that have persisted in high-disturbance environments (ex. storms, fires, glaciers) are less sensitive to edge effects (species sensitive to disturbance already lost by natural selection)

What are metapopulations?

collection of subpopulations connected by the movement of individuals

what can impact metapopulations within patches?

• resource availability

• size/shape of the patch

• increased genetic drift

• life history (density effects for mating)

What can impact population connectivity among patches?

• barriers

• distance

  • types of intervening matrix (urban vs rural)

What is the mainland-island model of metapopulations?

when a large, stable population (the source) acts as a continuous source of individuals that disperse to smaller, isolated populations (sink)

How do sink populations within metapopulations persist?

solely because of immigration from source populaton

In what ways does habitat loss impact all levels of biological diversity?

• local extinction

• population declines from loss of resources

• reduced genetic diversity

How does habitat loss impact community and ecosystems?

• changes in species interactions, ex. increased competition

• decreased connectivity between patches

• less nutrient retention

How can habitat loss impact human well-being?

• decreased ecosystem services ex. air quality, water purification, aesthetic value, reduced pollination

• increased aridity

• increased pollution

• reduced crop yields

How does population size on islands and patches correlate to immigration and extinction rates over time?

• low population: high immigration, low extinction

• high population: high extinction rates

Are extinction rates on large patches or small patches higher? How is the immigration rate?

higher extinction rates on small patches. equal immigration rates

Are immigration rates higher for far or near islands/patches? How is the extinction rate?

Higher immigration rates for far islands, but equal extinction rates

How does population size change with habitat area?

Population size increases logistically with habitat area

Why is experimental fragmentation important?

• can control for influencing habitats (ex. rivers), pollution, climate, cause

• can vary size/edge/isolation

• can replicate

What are consistent effects of fragmentation across all sizes/habitats/isolation?

• decreased diversity

• loss of specialists

• simpler/less resilient communities

  • extinction debt

What is extinction debt?

future extinction of species due to events in past ex. fragmentation, reducing long term species richness

How does reduced fragment area affect patches?

• reduced species persistence

• reduced species richness

• reduced nutrient retention

• changes to success rate

• changes to trophic dunamics

How does increased isolation in fragments affect patches?

• reduced movement between fragments

• reduced abundance

• reduced species richness

• reduced pollination

• changes to microclimate

• reduced nutrient retention

How does increasing edge affect patches?

• degraded community composition

• changes in trophic dynamics

What is immigration lag?

a delay in the arrival and establishment of new species into a habitat following a disturbance or environmental change, resulting in a decrease in species richness

What is ecosystem function debt?

the delayed loss of biomass and nutrient cycling after a disturbance/fragmentation

What are some approaches to habitat management?

• land sparing

• land sharing

What is land sparing?

conservation strategy that aims to maximize biodiversity by setting aside areas of land for nature while intensifying agriculture on other areas to meet food production needs. The idea is to create a clear distinction between high-yield farming areas and untouched natural habitats, rather than mixing conservation efforts within farmland

What is land sharing?

conservation strategy that integrates biodiversity conservation with agriculture by creating wildlife-friendly farming practices. Instead of separating high-intensity farming and natural habitats (as in land sparing), land sharing involves using lower-intensity, sustainable farming methods that allow wildlife to coexist with agriculture

What are benefits of a single patch?

• large core habitat

• positive alle effects

• habitat homogeneity

What are benefits and downsides of several small habitats?

• local extinction

• lower diversity

• decreased connectivity

• resilience to disturbance events

• reduced habitat homogeneity

What are the historical effects of racial redlining?

• luxury effect - positive relationship between affluence and biodiversity

• legacy effect - environmental changes result from historical human activities