New research shows that 21st century British woodlands are less distinctive than those of the early 20th century due to environmental change. Native woodland plants have re-organised over the last 70 years in response to increased soil fertility and loss of light related to increased canopy shading.
The research was carried out by a team from Bournemouth University, Natural England and the Centre for Ecology & Hydrology and will be published online in Proceedings of the Royal Society B (FirstCite website) on 22nd July 2009.
Lead author, Sally Keith of Bournemouth University, said: “We have identified the loss of unique communities within British woodlands through a comprehensive large-scale study of woodland plants. The results show that we must monitor biodiversity at the landscape scale, as well as gain a better understanding of processes affecting our native flora, if we are to conserve and restore the character of the traditional British woodland.”
The researchers investigated changes in the flora of British woodlands over seven decades with the study providing evidence of a new kind of biodiversity loss, namely a loss of the unique character of individual woods which had developed over centuries in response to local conditions. They found that the woodlands are more similar to each other now, when compared with 70 years ago, even though the number of plant species in each woodland had not fallen.
Co-author Professor James Bullock from the Centre for Ecology & Hydrology said: “This study shows that increased pollution and poor countryside management has led to increasing homogenization of biodiversity in British woodlands. These two issues must be addressed in future if we wish to restore the diverse woodland communities of the past.”
The study relied on a comparison between new field results and a historic dataset recorded over 70 years ago. In the 1930s, Professor Ronald Good cycled around Dorset and recorded the presence of plants at over 7,000 sites. The Dorset Environmental Records Centre (DERC) provided the research team with access to the historical data, and the scientists re-surveyed a subset of Professor Good’s woodland sites, visiting 86 woodlands across Dorset from late spring to early summer in 2008, recording the presence of plants as they are now. They then compared the plant records from the 1930s and the 21st century to see if and how the woodlands had changed.
The results indicated that, whilst the average number of plant species within each woodland remained the same, the difference between woodlands was significantly reduced. The researchers concluded that the woodlands that exist now are only a subset of the variety that could be seen in the 1930s. This process of increased similarity between ecological communities (groups of species in one site) is called ‘biotic homogenization.’
Biotic homogenization has major implications for biodiversity conservation as it is related to the loss of unique species combinations leaving an impoverished version of the past variety of nature. Other documented observations of homogenization have been caused by the introduction of non-native species; however this study concluded that the impact of non-natives was negligible. The results demonstrate that homogenization can occur simply through a re-organisation of native species, potentially suggesting the phenomenon may be more widespread than previously imagined.
The characteristics of the 2008 plant communities indicated that the soil was more fertile than in the 1930’s - a side-effect of the use of fertilisers in agriculture and its effect on the surrounding woodland. The composition of the plant communities also indicated that there was now less light available in the woods than in the past. This light loss is probably associated with the decline in traditional practices such as coppicing, which creates openings in the woodland as trees are harvested, leading to decreased woodland management.
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