In the UK, the area of wetlands increased by about 6 per cent between 1984 and 1990 to around 300,000 hectares. When precipitation levels exceed the soil's capacity to absorb water, soil and soil nutrients are carried away in streams and gullies. When the soil is very dry, the top-soil can be blown away in the wind. Can lead to nutrient depletion and lack of adequate soil structure for growth of plants. In Canada, erosion from cropland remained roughly constant over the same period.
Oil spills can cause problems for wildlife.
The increase in the area of forested land in Britain is largely a consequence of government subsidies to and direct control over forestry and is not necessarily an indication that biological diversity has increased because much of this additional forest is monoculture. The decline in soil erosion in the US is in part the result of a federal programme to subsidise the retirement of cropland at high risk of erosion. However, this programme largely replicates what would happen if subsidies to agricultural production were removed - because it is these subsidies that encourage usage of marginal land in the first place. A more important reason for the decline in soil erosion is the use of more modern farming practices, including crop rotation, interseeding and the planting of winter crops. The increase in the area of wetlands in the UK follows a long period of decline caused in large part by subsidies to agriculture and even subsidies to drainage.