Habitat fragmentation and degradation Flashcards
What is habitat degradation?
a reduction in the quality of habitat
- includes pollution and activities leading to desertification, erosion and sedimentation
What is habitat fragmentation?
larger continuous habitat becomes divided into smaller patches
- reduces habitat area but also changes structure of remaining habitat
Types of habitat degradation
- pollution
- desertification
- erosion & sedimentation
What is the largest environmental cause of human disease and premature death?
pollution
How many deaths does pollution cause pa?
9 million (16% of all deaths worldwide)
Types of pollutions
- pesticides
- oil spills
- toxic metals
- eutrophication
- acid rain
- pharmaceuticals
- plastics
- light, sounds and smell pollution
When were pesticides brought to the world’s attention? (pollution)
1962 by Racheal Carson’s book ‘Silent Spring’
What is DDT (pesticides - pollution)?
Bioaccumulation
banned across most of world
Why are agrochemicals harmful? and testing agrochemicals? (pesticides - pollution)
- kill non-target species & remove natural predators and further increasing reliance on agrochemicals
- undergo tests to investigate their toxicity to a standard suite of organisms - sub lethal effects (or effects on other organisms) not tested for
Neonicotinoids (pesticides - pollution)
- widely used - controversial
- sublethal effects on bee behaviour by impairing foraging behaviour, homing success, navigation performance and social communication - makes bees ‘drunk’
- banned in UK and EU, but farmers can be granted exemptions
Effect of oil spills? (oil spills- pollution)
- directly kills many species
- clear-up processes e.g. chemicals dispersants can cause further damage
What are toxic metals a result of? (Toxic metals- pollution)
- often result from manufacture, and directly kill many species
- often bioaccumulate
What is eutrophication? (Eutrophication- pollution)
adding fertilisers (nitrates and phosphates) to aquatic systems
What does eutrophication cause? (Eutrophication- pollution)
algal blooms - shade bottom-dwelling plants and decomposition uses up oxygen
‘Dead zones’ in coastal habitats (Eutrophication- pollution)
- 245,000 km2 of ‘dead zone’ in >400 coastal habitats around the world
Long-term effect of eutrophication on ecosystems (Eutrophication- pollution)
can be difficult for ecosystems to recover, even if pollution is removed
How is acid rain produced and its effects? (Acid rain- pollution)
- Nitrogen and sulphur released into ai form nitric and sulphuric acids, lower pH of rainwater
- can kill plants & animals
- can travel hundreds of miles, effecting ‘pristine’ ecosystems
Pattern of acid rain in the world (Eutrophication- pollution)
- reducing in Europe and North America
- increasing in East and South Asia
Examples of pharmaceuticals (Pharmaceuticals - pollution)
e.g. medicines, cosmetics, disinfectants, detergents
Effects of pharmaceuticals (Pharmaceuticals - pollution)
- emerging pollutant source - little is known about consequences
- antimicrobial resistance can be caused by antibiotic misuse (e.g. antibiotic resistant TB)
- hormones e.g. from contraceptive pills can impact on aquatic animal reproduction (e.g. shrunken gonads)
Plastics as a pollutant (Plastics - pollution)
- fast-growing form of environmental pollution
- problematic in marine ecosystems - get washed in from land
- more than 5 trillion pieces of plastic weighing > 250,000 tons are afloat in the world’s oceans
- can be mistaken for food, and break down releasing toxins
- microplastics are another emerging pollutant
Effects of light, sound and smell pollution? (light, sound and smell - pollution)
- affect behaviour
Effect of light pollution (light, sound and smell - pollution)
- light pollution - impacts circadian rhythms and disrupts normal feeding and breeding behaviour
- e.g. street lighting leads to 47% decline in moth caterpillar abundance in hedgerows and 33% decline in grass margins
- disrupts nocturnal feeding behaviour and likely disrupts egg-laying behaviour
Effect of sound pollution (light, sound and smell - pollution)
- impacts vocal communication, orientation and foraging
- e.g. blue whale forging is disrupted by boat traffic
- increasing evidence from marine and terrestrial species
Effect of smell pollution (light, sound and smell - pollution)
- little investigation but pollution can most likely disrupt natural scent communication (reproduction, social behaviour)
Examples, cause, and effect of desertification (Habitat degradation)
- poor soil and water management -> further drying of already dry areas
- pre-history, the Sahara was grassland
- rates of desertification are increasing
- e.g. The Mesopotamian Marshes, Iraq were drained by Saddam Hussein - now in the process of restoration
- most cases are not on purpose e.g. Aral Sea -> was 4th largest inland lake; irrigation upstream for cotton production drained it in 30 years; led to ecosystem collapse and human tragedy; restoration has started but has a long way to go
What are the current rates of soil erosion, in relation to previous levels? (Erosion & sedimentation - Habitat degradation)
- current rates of soil erosion are 11-38 times faster than previous levels
What causes erosion and sedimentation? (Erosion & sedimentation - Habitat degradation)
due to deforestation, overgrazing, and unsustainable agricultural methods
Cause of erosion & sedimentation (Erosion & sedimentation - Habitat degradation)
- causes degradation of agricultural land, and deposition of soil chokes up natural landscapes
Solutions for habitat degradation
solutions lie in environmental regulation at local, national and international levels
what is habitat fragmentation and what is it associated with?
divides larger habitat into smaller pieces
associated with habitat loss, but leads to specific biological consequences
Types of variation in patch and what it leads to (Habitat degradation - Biological consequences)
variation in patch:
- size
- shape (amount of edge)
- number
- isolation
leads to variation in species responses
Effect of habitat fragmentation (Habitat degradation - Biological consequences)
mostly negative but can be beneficial for some species in some situations
What is the relationship between habitat fragmentation and habitat loss? (Habitat degradation - Biological consequences)
aspects of habitat fragmentation do not correlate linearly with habitat loss
- mean patch size - negative correlation
- number of patches - bell-like curve
- total edge habitat - bell-like curve
- mean nearest neighbour distance - steep decline, then slower decline over time
Species richness equation
S=CA^Z
S=species richness
A=habitat area
C=constant that depends on the unit of measured used
exponent of Z is scaling factor that dictates how species richness changes with area
What are extinction thresholds? (Habitat degradation - Biological consequences)
Species have extinction thresholds - minimum habitat size that are required for them to persist
What are allele effects? (Habitat degradation - Biological consequences)
small populations are disproportionately likely to go extinct. Need to find mates, dilution effects from predators etc.
Behavioural aspects can have a big effect on these
What are edge effects? (Habitat degradation - Biological consequences)
Smaller patches have proportionately more edge, as do more elongated patches
- e.g. a Haddad et al. (2015) found that 70% of world’s remaining forest is within 1 km of forest edge, and nearly 20% is within 100 m of an edge
Edge habitats (Habitat degradation - Biological consequences)
- less resilient (more changeable conditions)
- vulnerable to invasive species
- behaviour of specific species involved is key to determining which will thrive and which will decline
- dominated by generalists that adapt well to anthropogenic landscapes
- predation often high (e.g. by corvids and domestic cats)
Human-wild life conflict (Habitat degradation - Biological consequences)
- related to habitat loss, increased edges, anthropogenic food sources
- understanding traits of animals and humans that are of greater risk is important
- In Asian elephants, human mortality occurs mostly while chasing wild elephants using firecrackers. Lone male elephants are more likely to attack people
- behavioural solutions can be important e.g. using beehive fences to deter elephants
Patch isolation (Habitat degradation - Biological consequences)
- increases with fragmentation
- behaviour is important here
What does the ability to disperse between patches depend on? (Habitat degradation - Biological consequences)
- distance between patches
- hostility of the environment
What does increased connectivity between patches affect? (Habitat degradation - Biological consequences)
reduces probability of reaching extinction threshold
can reduce genetic diversity and increase risk of local extinction
Solutions for patch isolation (Habitat degradation - Biological consequences)
- different solutions may be required for species with different characteristics
- some solutions may be better for a wider range of species
Island Biogeography Theory - MacArthur & Wilson (1963)
What is the expected species diversity of ‘island’ related to? (applications for landscape-scale conservation)
- The distance of the island from the mainland
- Island size
- The number of species on the mainland that are not already on the island
What is the Island Biogeography Theory? (applications for landscape-scale conservation)
- larger ‘Islands’ = higher species richness (lower extinction)
- larger reserves should be better than smaller ones
- but single large reserve always better than two smaller ones?
- not necessarily e.g. are they preserving common or scarce habitats? Are they preserving different habitat types or species?
Effect of species richness on ‘Islands’ close to ‘mainland’? (applications for landscape-scale conservation)
- ‘Islands’ close to ‘mainland’ are likely to have a greater species richness due to increased dispersal
What is best in the Island Biogeography Theory? (applications for landscape-scale conservation)
- Having a network or reserves with dispersal corridors is best
- Create a metapopulation
Metapopulation models (applications for landscape-scale conservation)
- ‘Islands’ varying in size and quality
- Dispersal can occur between them
- Source populations have expanding populations and supply dispersers
- sink populations have contracting populations
- can create mathematical models of real landscapes to design effective reserve networks
Applications for landscape-scale conservation
- identify source and sink populations
- identify areas in need of habitat restoration
- create corridors or stepping stones to aid dispersal
- decide on size and shape of nature reserves: larger, more circular, but need to be appropriate for landscape and incorporate target habitats
