- Increased contrast in the UK’s climate – the currently dry south east will become drier, and north will become wetter. This could lead to drought in the South and increased flooding in the north. This is also likely to increase soil aridity, especially in the South, and a decrease in crop yields in this area. However, in the North, it may actually prove beneficial for the timber industry: an increase of 25% by 2050 is predicted.
- Sea level is predicted to rise at rate of about 5cm per decade- this increase will be higher in the North, and lower in the south, as a result of isostatic change. This will further increase damage from storms, and coastal erosion.
Specifically, changes to vegetation are likely to include;
- Loss of montane plant communities
- Hearths may become subject to more frequent fires
- Wetland may dry out and frequently change species composition, especially due to human water abstraction.
- Coastal dunes and rocks may become invaded by alien species such as the hottentot fig
- Salt marshes and brackish water habitats may be lost as sea level rises. Climate change will occur too rapidly for species to adapt in an evolutionary sense – so many species may become extinct.
- Drought may cause the loss of broadleaved woodland
- Species confined and dependent on particular areas of Britain may die out
- Salt marsh vegetation may decline
Specifically, global warming is likely to have an adverse effect on freshwater ecosystems. The problem is one of scale: Many of the most significant impacts on freshwater ecosystems will result from hydrological changes at the scales of small catchments and drainage basins.
Water levels in lakes and reservoirs are highly sensitive to weather conditions; small lakes and reservoirs may fluctuate rapidly in response to changes in precipitation and evapotranspiration. Where water levels are likely to decline, inshore areas will change significantly. In shallow lakes and reservoirs in particular, inshore aquatic vegetation and surrounding wetlands would decrease in area. This decrease may result in changed habitats for aquatic biota, reduction of productivity, and even extinction of fish and invertebrate species that are dependent on these types of biomes. Where lakes have extensive bordering wetlands, declining water levels would reduce productivity and impact negatively on populations of fish and invertebrates that are dependent on these types of wetlands for their survival.
Increased eutrophication can be expected—with high production of aquatic biomass, decreasing species diversity, deterioration of oxygen conditions, and adverse effects on water quality. In regions where most drinking water comes from surface sources, decreasing lake volumes and lower water quality may cause serious problems for human use.
Another human impact on vegetation (particularly in National parks) is trampling and footpath erosion. Physical trampling of vegetation can cause physiological changes in plants themselves, damaging leaves and reducing their size and number. This reduces food reserves, leading to a reduction in growth, size, flowering and fruiting. However, different species of plant react differently to trampling. This can lead to changes in the whole plant community, reducing the total number of species and altering plant composition to a flora typical of trampled areas. These new plant communities are usually made up of species better able to cope with trampling, such as annual meadow-grass and broad-leaved plantain. In some cases, this change can be a big problem, for example when an area is important for its flora. Another major impact of trampling is increased susceptibility to erosion. With the removal of vegetation, plant cover is reduced and underlying soils become exposed. As the soil becomes scuffed, small particles are washed or blown away. This leads to increase soil erosion. The severity of erosion depends on the soil type, with deep, fine-grained, waterlogged and organic soils especially sensitive.
Another human activity which effects plant communities (particularly in LEDCs) is desertification; a combined effect of overgrazing, soil erosion and deforestation, which has had a particularly devastating effect on the poorest areas of Africa.
It has been estimated that 34% of the surface area of Africa is under the threat of desertification. This is equivalent to four-fifths of the ASAL areas of Africa. Desertification affects three principal areas of the continent, namely, Mediterranean Africa, the Sudano-Sahelian region and Africa south of the Sudano-Sahelian.
The key problem is soil erosion. Soil, the thin layer of top-soil on which our survival depends, is a non-renewable resource. For nature to form a layer of top-soil thick enough to support plant life takes thousands of years. Through human misuse, the layer can be destroyed in a few decades, or in a few years. Once eroded, its loss is permanent. That is desertification.
The encroachment of cultivation on these vulnerable lands has led to loss of biodiversity and accelerated soil erosion, making the people even more vulnerable to future droughts.
The reduced capacity for food production as a result of vegetation loss has brought a population of over 200 million people to the verge of calamity. Some have died of starvation, and among the survivors, especially the children and young people, many will suffer impaired health for the rest of their lives.
Overall, the main human impacts on plant communities are global warming, trampling, and desertification. This is, in general leading to a decrease in biodiversity, and a complete change in the makeup of plant communities. The ironic thing is, that in some areas (such as Africa) this human impact, is actually causing more problems in the long run than it had caused solutions in the short run.
