CHAPTER 4: THREATS TO BIODIVERSITY (Effects on Biodiversity (Reduced…
CHAPTER 4: THREATS TO BIODIVERSITY
Habitat Modification and Destruction
The clearing of habitat for agriculture, urban or other developments. Destruction can be broadscale clearing or
fragmentation of habitats
Fragmentation of habitat
= Remaining remnants may be too small to support viable populations of some species.
Reduction in quality of a habitat.
Both habitat modification and degradation caused by events such as change in fire regimes, salinisation, drainage and erosion.
: Species that have been purposely or accidentally imported into a new region. Introduces species compete with indigenous species for ecological niches.
In Aus, introduced species:
(e.g European red fox) contributed to the disappearance of remnant populations of endangered mammals + affect malleefowl.)
(E.g intro exotic herbivores (feral pigs, rabbits, cattle, goats, buffalo) result in land degradation.)
Plants introduced(e.g C.monilifera) become environmental weeds --> replace native plants eliminate native animal species that depend on native plants for food and shelter.
Many inland waterways clogged with introduced water plants (e.g water hyacinth and salvinia)
Intro fish affected some rivers (e.g European carp, trout)
Threats to Biodiversity
predictions of species population survival using probabilities including likelihood of extinction
human and non-human threats to biodiversity including: creation and isolation of small populations through habitat modification and over-exploitation; genetic swamping, inbreeding, and demographic variation due to small population size; loss of pollinators, dispersal agents, host species or symbionts that affect reproduction and persistence of species; bioaccumulation that concentrates environmental poisons in food chains; and exotic species that compete for habitat, shelter and food
Overexploitation of Plant and Animal Species
: Result of human harvesting food or the use of natural resources from forests, fisheries, and wildlife above the sustainable level. Results in degradation and loss of habitats and ecosystems and the reduction of the population of a species --> vulnerable to disease and other changes.
Pollution of soil, water and atmosphere
(contaminants move up the food chain and accumulate in high order predators) --> has severe implications for survival of higher level predators.
E.g Acid rain --> made lakes lifeless and damaged forests.
Global Climate Change
Alter ecosystem structure and function, cause adverse effects on biodiversity.
Depends on whether the organisms can adapt to the changes; the rate at which the change occurs and whether species can move to more suitable areas as their natural habitat changes.
higher impact on species in remnant or fragmented habitats
cause sea level rise --> affect coastlines and completely submerge many islands, species become extinct
Effects on Biodiversity
: The complete disappearance of a species or of a local population.
Accelerated extinction is largely increasing over the natural rate of extinction.
Loss of Symbiotic Organisms
: Loss of organisms that are critical to the survival of other organisms.
Different species live together in an intimate association.
: The parasite lives in or on the host, and derives food or resources from the host to the point of harming or killing it.
: An interaction where one species benefits from the relationship whilst the other species gains no benefits nor harmed.
Mutualism: Two species live together and both derive benefit from one another
Reduced Population Size
Small population size will have less genetic diversity than the previous larger population. --> reduced chance of adapting to changes in the environment.
Organisms with the gene that is most advantageous to survival will pass on their genes to the next generation.
Allele frequency in a population is determined by random events rather than by natural selection.
: Breeding between individuals that are genetically related.Reduces survival rates and reproductive success of members in population.(inbreeding depression)
: Environmental disruption caused by human activity cause populations that were once geographically isolated to come into contact with one another. Both populations may interbreed and produce hybrids (e.g zonkey). The genetic swamping occurs when one of the interbreeding population is small and the no. of hybrids is large --> genes of bigger population spread throughout the smaller. Genetic diversity of smaller pop is lost.
: The chance variation in the population (operating on a number of different factors: birth rate, death rate, sex ratio). Chance variation away from the average is greater in small populations than in big populations.