Nature can rewild itself but humans need to help by removing invasive species, cleaning up pollution and reducing over-grazing, writes Jonny Hughes.
Globalisation continues to homogenise the high street. Go to any town in the UK and the same shops, cafes and burger chains will be there, selling the same products for the same prices. A similar process is happening in nature.
The spread of humans across the world has been a boon for rats, pigeons and other generalist species that quickly adapt to changing environmental conditions and thrive in a variety of disturbed habitats. But, just as independent shops are being squeezed from the high street by multinationals, specialist species which need good quality, undamaged and unpolluted habitats are suffering steep declines on every continent.
Populations of generalist birds like the chaffinch, blackbird and wood pigeon are relatively stable or even increasing in some areas. Contrast this with specialists such as the capercaillie, corncrake, curlew and several seabird species whose numbers remain perilously low and who may already have been lost from Scotland if it wasn’t for the efforts of conservationists.
As people and goods increasingly move around the world we also introduce non-native species into ecosystems already made vulnerable through development pressures, conversion to agriculture or pollution. Some non-native species have become highly invasive, faring even better in their new world than native generalists.
Since its introduction from North America, the grey squirrel has replaced the red across the whole of the Central Belt and would have spread considerably further if it wasn’t for the Saving Scotland’s Red Squirrels project, a partnership led by the Scottish Wildlife Trust. Plants such as Japanese knotweed, Himalayan balsam and giant hogweed run riot along many rivers, causing widespread economic and ecological damage.
One of the most successful invaders is also one of the most beautiful: rhododendron ponticum whose lilac blooms brighten up the roadsides of the west coast in early spring. Unfortunately, rhododendron chokes the life out of the oak, birch and hazel Celtic rainforests of the west coast. Warm and wet Atlantic weather fronts create ideal conditions for the growth of lower plants like mosses, liverworts and lichens. There are more species of lower plants in some of the wooded ravines of the west coast than there are in many tropical rainforests.
These oceanwoods are places of truly international importance. So well done to the National Trust for Scotland for sending a team of abseilers into Corrieshalloch Gorge recently in a bid to remove invasive plants including rhododendron ponticum and Japanese knotweed.
We urgently need many more such projects to be planned and carried out on big scales, preferably at river catchment level. There is little point in taking out giant hogweed downstream while leaving colonies upstream to constantly reinvade. Similarly, rhododendron ponticum removal has to be total, otherwise it quickly returns, shading out native plants and poisoning the soil as it does so.
The good news is that removing invasive plants, if done methodically, does seem to work. Recent research led by the James Hutton Institute found that 15 years after removal of rhododendron ponticum from an Atlantic oak wood, characteristic mosses and liverworts made a dramatic comeback.
The lesson here is that if we want to save all of nature, not just those resilient species that can adapt to our lifestyles, we need to make habitats more natural again. This means removing pollution, eradicating non-native species and reducing overgrazing before letting nature get on with rewilding itself.
Jonny Hughes is chief executive of the Scottish Wildlife Trust. Follow him on Twitter @JonnyEcology