Using named examples assess the severity of global and local threats to biodiversity

Biodiversity refers to the variety of species within an ecosystem and is something which is under increasing threats on both a local and global scale. An example of a global threat to biodiversity is desertification. Desertification is the process by which fertile, arable, land loses nutrients and life becoming barren. The Sahel region is an area which has been massively affected by desertification, especially since the 1950’s when farmers and other locals began to move into the areas which were habitable and used them as farmland. The farmers allowed their cattle to graze freely which resulted in overgrazing and thus having a severe impact on the biodiversity of the land as many plant species were grazed out of an area by the livestock. This loss of plant life due to over grazing has not only resulted in the immediate short term damage to biodiversity but also long term damage as the top soil loses all anchorage from the plant roots causing it to blow away or be washed away leaving bare rock which plants can’t grow on naturally in the future. Due to both the short and long term effects of desertification I believe it is one of the most severe threats to biodiversity on a global scale.

Another global threat to biodiversity is climate change. Climate change is the changing of global temperatures over a long term scale, primarily caused by the greenhouse effect and the enhanced greenhouse effect. Oceans are especially susceptible to climate change as they have not only the most climate sensitive life but also act as a massive carbon and heat sink meaning effects are felt most severely here. Climate change threatens marine biodiversity by altering the temperature and acidity of the waters. The ocean is also home to one of the most concentrated, diverse and vulnerable habitats in the world, the coral reefs. The Coral Triangle, located in the western Pacific, is one of the most important coral reefs with over 120 million people being directly sustained by the marine and coastal resources of the coral triangle. The annual, maximum and minimum temperatures of the oceans surrounding the coastal areas of the Coral Triangle are warming significantly (0.09-0.12 ° C per decade) and are projected to increase by 1-4°C toward the end of this century, an increase of more than 2°C will eliminate most coral reef systems. Climate change poses the most severe threat to global biodiversity because not only does it primarily effect the most vulnerable habitats but it’s effects are felt throughout all habitats and everyone who is dependent on them.

An example of a local threat to biodiversity is the invasion of alien species, essentially this is when a non-native species moves into a habitat, causing species to die out in four different ways. Firstly, some species change the habitat which other species are reliant on, for example, when the Asian chestnut blight fungus virtually eliminated American chestnut from over 180 million acres of eastern United States forests in the first half of the 20th century, it was a disaster for many animals that were highly adapted to live in forests dominated by this tree species. For example, ten moth species that could live only on chestnut trees became extinct. Another way alien species can result in loss of other species is through hunting for food, for example, the first sailors to land on the remote Atlantic island of St. Helena in the 16th century introduced goats, which quickly extinguished over half the endemic plant species. The third way alien species can result in the loss of another species is by out competing for resources, for example, North American grey squirrels are driving native red squirrels to extinction in Great Britain and Italy by foraging for nuts more efficiently than the native species. The final way an alien species can cause the extinction of another species is through hybridisation. Hybridisation, or cross-breeding, of introduced species with natives gradually leads to the extinction of many native species, as their gene pools inevitably evolve to become those of the invader. Introduced mallards are driving the native Hawaiian duck to a sort of genetic extinction by breeding with them. The invasion of non-native species poses a fairly large threat to local biodiversity however as most species arrive because of humans it is easier to manage than other threats making it less severe.

Another local threat to biodiversity is the over exploiting and harmful methods of exploiting wildlife. In Africa, the Black Rhino is a species which has been hunted to the point of being almost extinct in the wild. Between 1970 and 1992, 96% of Africa’s remaining Black Rhinos were hunted, primarily for their horns which can be sold on black markets for up to $100,000. The over hunting of this species has meant that not only has the Black Rhino almost been wiped out but any species which may rely on the Black Rhino also faces a major threat. Conservation efforts for the protection of this species have been far more difficult than normal due to the political instability of the region forcing issues such as the over hunting of species being pushed to the side lines. While this has a very severe impact on one or two species the overall damage to the biodiversity of the ecosystem is relatively minor. Harmful methods of exploiting resources, primarily fishing, are having a far more severe impact on the biodiversity of marine ecosystems because of the colossal amounts of collateral damage to other local species and habitats. Cyanide fishing is designed to stun the fish so that they can be caught easily however the damage to the habitats is huge as, on average, for every live fish caught by cyanide fishing 1 metre square of coral reef is destroyed. Another harmful method of fishing is through bottom trawling where huge heavy nets are dragged along seabed however this destroys a lot of the habitats and catches a lot of extra fish which weren’t intended to be caught and will be thrown away. Actions to prevent this are being taken through quotas which fisheries can’t exceed and through sustainable yield management in Southern Ocean Fisheries, we are trying to mitigate the impacts of over and harmful fishing. Harmful fishing has very severe impacts on biodiversity on a local scale as not only do the targeted species get affected by the surrounding species and their habitats are also destroyed which poses a huge threat to the eco system as a whole.

In conclusion I believe that global threats to biodiversity are more severe than local threats as the sheer amount of ecosystems whose biodiversity is affected is far greater and the effects typically hit the entire ecosystem, as opposed to local threats such as over harvesting which typically only hit a smaller number of species thus having a less severe impact on the biodiversity of an ecosystem as a whole compared to global threats such as global warming.