Nottinghamshire Wildlife Trust: News of breeding success tempered by worries over long-term impacts of climate change
Following the county’s first ever recorded breeding successes of great white and cattle egret at Nottinghamshire Wildlife Trust’s Besthorpe Nature Reserve last summer, the trust recently announced that both species have successfully fledged young at the site again this year, writes Erin McDaid, of the Nottinghamshire Wildlife Trust.
This exciting news comes little over a decade since the reserve, which sits alongside the Trent between the villages of Collingham and Besthorpe in the Trent Vale, saw the first ever Nottinghamshire breeding of little egrets back in 2013. That all three species now appear to have become established as breeding birds at the reserve is clearly a story of success — underlining nature's resilience and adaptability — and is proof positive that nature reserves are vital to species’ recovery.
However, delight at the birds success is somewhat tempered by the fact that until just a couple of decades ago you'd likely have had to venture to southern Europe to find a site where all three species were regularly rearing young.
As naturalists it is always exciting to welcome new species, but the fact that they were once confined to much more southerly locations — such as the Doñana National Park, or the Camargue region of southern France — serves as a real life reminder that changes in our climate are affecting wildlife. Some 20 years ago I remember excitedly watching egrets for the first time at a nature reserve on the Catalan Coast in Spain — now I can see them year-round here in the Trent Valley.
As climate warms, species that prefer higher temperatures may well be able to colonise new areas, taking advantage of the increased warmth, but when temperatures reach levels where they have a negative effect, species have only two options. They can either seek cooler temperatures at higher altitudes or greater latitudes — essentially, they can head up mountains or head north.
Whilst highly mobile species such as butterflies and birds can adapt much more quickly due to their ability to travel great distances, other species are less able to cope. Plants can colonise via seed dispersal, but this is far more hit and miss approach and species that spread via underground roots and rhizomes can take decades to move just a few feet, meaning they are unlikely to be able to adapt to the speed of climate change we are currently experiencing. As a result, species such as our cherished bluebells face an uncertain future.
Even the most mobile of species face added barriers. Moving to higher ground may not be possible for species that favour marsh or maritime habitats, and not all species are designed to traverse open seas.
Butterflies that migrate over significant distances do so over weeks and months — with successive generations having to complete a full life-cycle from egg, through caterpillar and chrysalis until once again reaching their flying form before embarking on the next leg. This journey also requires the presence of suitable food plants at every stage. For every species that has made a successful move north to become established on our shores we have to consider those that were once present but now rarer due to climate change. Whilst the comma butterfly has benefitted — expanding its range from the south-west of England up to Scotland, the speckled wood has been slower to move northwards due to the patchy availability of its preferred woodland habitat. Species that prefer cooler climes have struggled with local extinctions resulting from sites becoming too hot and dry. The mountain ringlet has been particularly badly affected and is now absent from a third of its earlier strongholds.
We must also question whether the northward movement of species is merely evidence of opportunism or a signal that conditions in their traditional heartlands are becoming harsher and inhospitable. It is feared that the breeding range of many wetland bird species is likely to contract ,and vital wetland sites such as Doñana National Park in Andalusia are in danger of drying out due to increasingly severe and frequent droughts and over abstraction of water for agriculture. So, whilst the naturalist in all of us may rejoice when new species become established in our midst, our inner environmentalist should signal caution as to the changes that are driving their movement.
As well as highlighting nature’s capacity to adapt, the recent colonisation of Besthorpe by a trio of egret species also underlines the need to ensure that we continue to care for, create and link wetlands and other habitats to give wildlife ever chance of adapting as our climate continues to change.
For further details about Besthorpe Nature Reserve, visit nottinghamshirewildlife.org/nature-reserves.