Habitat degradation and fragmentation Flashcards
what is habitat degradation
a reduction in the quality of a habitat as a result of pollution and activities leading to desertification, erosion and sedimentation
what is habitat fragmentation
when larger continuous habitats become divided into smaller patches which can initiate a cascade of changes in the configuration of landscapes
what is the main cause of habitat degradation
Pollution, commonly caused by pecticdes, herbicides, sewage, fertilizers from agricultural fields
largest environmental cause of human disease and premature death
list some of the different pollution types which contribute to habitat degradation
- pesticides
- oil spills
- toxic metals
- eutrophication
- acid rain
- pharmaceuticals
- plastics
- light, sound and smell
outline how pesticide pollution can cause habitat degradation
- brought to attention by Rachel Carson 1962
- explained the issue of DDT causing bioaccumulation in the trophic systems reducing biodiversity
- since been banned across most of the world
- despite learned lessons harmful pesticides still used with non target effects with sub lethal effects which are not investigated
outline the case study on the sub lethal effects pesticides have on bees affecting foraging behaviour, homing success and navigation performance
neonics are the most widley used insecticide in the world, they are still toxic but less so than others
spread to all aspect of plant including pollen and nectar, they dont kill the bee but have sublethal affects e.g. in bumble bee queens when exposed they are 26% less likley to lay eggs increasing risk of population extinction by 28%
outline how oil spills and toxic metal pollution can affect habitat degradation
1) directly kills many species and often the clear-up processes such as chemical dispersants cause even further damage
2) often result from manufacture and directly kill many species however ingestion or inhalation can lead to accumulation of contaminates in tissues causing DNA damage, compromised immune function and cardiac dysfunction
how does eutrophication contribute to habitat degradation
the addition of fertilisers such as nitrates and phosphates causes increased growth of unwanted plants such as algal blooms which uses up oxygen killing off species creating dead zones made up of only tolerant species in the polluted waters
how does acid rain contribute to habitat degradation
nitrogen and sulphur released into the air forms nitric and sulphuric acids which lower the PH of rain water killing plants and animals
- it can travel hundreds of miles effecting many ecosystems
outline how pharmaceutical pollution contributes to habitat degradation
e.g. medicenes, cosmetics, disinfectants and detergents
it is an emerging pollution source with little known about its consequences
hormones such as in contraceptive pill can impact aquatic animal reproduction
an important route is the excretion or improper disposal of medicines into plumbing and sewer systems from patients undergoing treatment
outline how plastic pollution contributes to habitat degradation
it is a fast growing for of environmental pollution and becomes particularly problematic in marine ecosystems
recent estimates suggest more than 5 trillion pieces of plastic weighing more than 250,00 tons afloat in the worlds oceans
outline how light, sound and smell pollution contributes to habitat degradation
affects behaviour
light= impacts circadian rhythms and disrupts normal feeding and breeding behaviours
e.g. street lights lead to 47% decline in moth caterpillar abundance in hedgerows
sound= impacts vocal communication, orientation and foraging e.g. blue whale foraging is disrupted by boat traffic
smell= little investigated but pollution can most likely disrupt natural scent communication
what is desertification
a form of habitat degradation where poor soil management practises lead to soil degradation that causes relatively dry areas of land to become increasingly arid and lose their water bodies, vegetation and wildlife
e.g.
Mesopotamian Marshes, Iraq were drained by Suddan Hussein but now in process of being restored
how is erosion contributing to habitat degradation
current rates of soil erosion are 11-38 times faster than previous levels due to deforestation, overgrazing and unsustainable agricultural methods resulting in degradation of agricultural land and deposition of soil chokes up natural landscapes
what are some solutions to habitat degradation
solution lie in environmental regulation at local, national and international levels
what are the biological consequences of habitat fragmentation
- extinction thresholds = minimal habitat size required for a species to persist
- allee effects = small populations are disproportionate likely to go extinct
- edge effects = smaller patches have more edges as do more elongated patches
- human wildlife conflict = related to habitat loss, increased edges and anthropogenic food sources
- patch isolation
what is an edge effect
edge habitats as reffered to as ecotones mark the transition between two different habitats
habitats are often less resilient with more changeable conditions
- more wind = negative biomass responce
- increased drought and fire = negative biomass responce
- increased light and nitrogen = positive biomass responce
what is the issue with patch isolation
isolation is a function of both distances between habitat patches and the matrix that separates those habitat patches such as hostility of environment
as distance between patches grows it becomes more difficult to disperse so successful migration is less likley
= habitat corridors can be provided
what is the island biogeography model and how can it be applied for landscape-scale conservation
it argues that the number of species on an island represents an equilibrium between two opposing processes of immigration and emigration and that the rate at which new species arrive at an island determined by
1) distance
2) island size
3) the number of species on the mainland that are not already on the islands
= larger islands have higher species richness therefore larger reserves should be better than smaller ones
= islands closer to mainland more likley to have greater species richness so reserves with dispersal corridors are best
what is a metapopulation model
a metapopulation is a collection of local populations which are spatially separated from each other in individual patches of landscape but connected to each other by dispersal and exchange of individuals
source populations= expanding populations and supply dispersals
sink populations= have contracting populations
how can a metapopulation model be applied for landscape scale conservation
1) identify source and sink populations
2) identify areas in need habitat restoration
3) create corridors or stepping stones to aid dispersal
4) decide on size and shape of nature reserves e.g. larger, more circular but also need to have appropriate landscaping and incorporate target habitats
