Global warming and Exmoor
Many experts now agree that global warming is a reality and largely the result of the burning of fossil fuels and the emission of pollutants into the atmosphere.
The emission of greenhouse gasses and climate change probably represents the greatest environmental threat facing Exmoor today. As a result of global warming there is an anticipated rise in winter rainfall, summer drought, storminess, sea level and flooding as well as a huge effect on biodiversity. Over the next fifty years annual temperatures locally are expected to rise by up to 2.3°C, compared with 0.3°C over the last hundred years. Temperatures in 2001 were the highest since global records began in 1859 and nine of the warmest years on record have been in the last ten years. The thermal growing season has been extending by over a day every twenty years and in 2000 the season lasted 330 days. The West Country seems to be getting warmer at a rate higher than the global average. In 2001 it was 6.2°C higher than its average for the previous 30 years.
Rainfall has been continuously recorded in Britain for over 250 years. The annual rainfall seems to broadly fluctuate with peaks and troughs roughly every 50 years. At present this is nearing the top of a peak, so rainfall appears to be increasing. It is too early to say whether it will continue to increase due to global warming. However, although the total rainfall each year appears to average roughly the same over a century, the distribution of rainfall through the year is changing, with summers becoming drier and winters wetter. There are rainfall records from many parts of Exmoor but none from within the National Park which are continuous enough to show long term climate change.
Changing climate will have an effect upon biodiversity. There will be an increase in some species now at the northern edge of their range, particularly in sea creatures and birds such as egrets and Dartford warblers. Relatively frost free winters will result in a general increase in cold blooded creatures, particularly insects. This will include many pests such as ticks. Some animals will no longer go into hibernation. This causes a problem with using up vital fat reserves and creatures such as dormice will be threatened. Many isolated communities of animals and plants will not survive as they cannot easily relocate. Beech trees are not drought resistant and those in hedgerows are particularly threatened by dry summers. An increase in moorland fires is also likely, with particular threats to blanket bog.
In Kyoto in 1997 EU member states agreed to reduce emissions of six greenhouse gasses. Whatever action can be taken to reduce air pollution will come mainly from Government policy, but local planning policies and development control will play a part. The Government has introduced regulations requiring District Councils to review and monitor air quality within their areas. They are required to set targets for traffic reduction. For Exmoor the implications of this will mainly be to support measures to: reduce vehicle emissions through attempting to reduce the number of vehicles on the roads and encouraging cleaner fuels; increase the use of renewable energy sources; increase broadleaved woodland cover in line with Biodiversity Action Plan targets. The trend on Exmoor is currently positive in all these respects.
Air pollution over the Bristol Channel, seen from County Gate
Sea level changes
Regardless of sea level changes, the land level of Exmoor is dropping. This is due to isostacy – the see-saw effect caused by the weight of ice on Britain during the Ice Age. The north of Britain sank under the weight of ice and now it is rising whilst the south is dropping. So relative sea level is increasing faster locally than globally. Sea level is expected to rise by up to 0.7 metre over the next 50 years compared with 0.2 metre over the last 90 years. Surprisingly, the height of tidal storm surges, like the one that breached the shingle ridge at Porlock Bay in 1996, will slightly reduce with global warming. The Bristol Channel is an exception in this case. The height of the highest third of waves has, however, increased by 15% over the last 20 years, so the rate of coastal erosion will increase.