Vegetation and soil

coastlineBiodiversity in the UK

Biodiversity describes the number of species of living organism within an ecosystem. Some biomes, notably the tropical rainforest, have much greater biodiversity than others (such as Arctic tundra or hot deserts). The climatic conditions promoting vegetation growth in an area are the primary determinant of how many niches exist in an ecosystem that can be occupied by living organisms.

In the UK's native deciduous forest, four-storey growth (canopy, shrub, field and ground layers) supports relatively high levels of biodiversity (especially for insects, animals and birds). However, lower levels of biodiversity are found in those regions of the UK where acidic grassland, heather moorland or coniferous forest dominate as a result of local conditions.

Rare species are sometimes found only in specific coastal environments such as sand dunes and salt marshes. These areas may be granted protected status as a site of special scientific interest (SSSI). Gardens and other human-maintained ecosystems can have unusually high levels of biodiversity for decorative or commercial reasons (estimates suggests British gardens may be home to as many as 15,000 plant species and varieties).

Biodiversity is often higher in an ecosystem during its earlier stages of development and growth, rather than when it reaches full maturity. This is because many ecological communities have the greatest number of species at an earlier stage of succession. In time, the field layer of flowering plants, ferns and grasses can become partially shaded out by a broad-leaved tree canopy, resulting in a fall-off in species richness due to competition for light.

What impact will climate change have on biodiversity in the UK?

The net impact of climate change on biodiversity is difficult to anticipate. Any loss of drought-stressed trees in exceptionally dry areas might adversely effect some bird and insect species. Yet tree death might actually increase local biodiversity as a greater range of flowering plants, grasses and forbs could survive once the dense shade of trees is removed (only 3% of sunlight reaches the ground beneath a dense broad-leaved canopy).

Several reports of changing biodiversity have emerged in recent years:

  • Garden owners found that indigenous herbaceous plant species such as phlox and lupin struggled to survive during recent heat-waves in 2004 and 2006. In contrast, exotic species such as yucca and olive thrived in the hot dry conditions experienced by southern England. While overall numbers of cultivated species may not decline, the structure of British garden communities is likely to change if gardeners start to favour plants of Mediterranean or Tropical origin that require lower maintenance.
  • Almost half of the UK's migratory birds have experienced a severe decline in numbers in recent decades. Scientists believe that this may reflect difficulties the birds face in adapting to changing conditions, both in the UK and in Africa where species such as the swallow spend winter.
  • Changes in marine biodiversity appear to be resulting from warming surface water temperatures (and associated changes in variables such as wave action and salinity). There have been more sightings of large animals such as whales, sharks and sea turtles in British waters.

Some coastal SSSIs face the greatest actual threat to biodiversity as result of climate change. In some instances, rare species will want to move as sea levels rise or rates of coastal erosion accelerate. However, they will be unable to migrate inland if their nature reserve is surrounded by monoculture (intensive agriculture) or urban settlement. In the long-term SSSIs may need to be enlarged and ultimately linked together to form one long biodiversity corridor as part of a sustainability strategy that will leave coastal ecosystems better placed to adapt and change in response to future climate change.

Student Practice Question:

Explain why species diversity can vary from place-to-place and from time-to-time.

In addition to explaining why different types of biome exist in different parts of the world, a good answer will volunteer ways in which climate change may now be effecting the biodiversity of UK ecosystems.