Following the county’s first ever recorded breeding successes of great white egret 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.
This exciting news comes little over a decade since the reserve, which sits alongside the River Trent between the villages of Collingham & Besthorpe in the Trent Vale, saw the first ever Notts breeding of little egrets back in 2013. That three species of egret have now bred at the reserve is clearly a story of success. It illustrates nature's resilience and adaptability in the face of ever increasing pressures and provides 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 that arrive of their own volition, but the fact that they were once confined to much more southerly locations the Doñana National Park in Spain or the Camargue region of southern France, serves as a real life reminder that changes in our climate are increasingly impacting wildlife. Over 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. This scale and speed of range expansion is neither normal nor without consequence.
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 – 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 strategy 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.
England is home to around half of the world’s bluebell population – meaning that if our climate were to become inhospitable to the species, their survival would be under threat.
Even the most mobile of species face added barriers. Moving to higher ground may not be a practical choice for species that favour marsh or maritime habitats, and not all species are able to traverse open seas.
Butterflies that migrate over significant distances do so over weeks and months - with successive generations having to complete their 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 an abundance of suitable food plants to be available at every stage along the route.
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.
The breeding ranges of many wetland bird species globally are forecast to contract in the coming decades, 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.
When considering what the future holds for species currently tracking north in search of new territory – simple facts of geography also come into play. Even a cursory look at a map of the northern hemisphere rams home the point that species that have already reached our shores due to climate change – or native species that have headed to Scotland in search of cooler climes – will soon run out of options when faced with open oceans and few remaining land masses to explore.
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 ability 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 every chance of adapting as our climate continues to change.
We must also embrace the power of nature to help species to adapt by restoring keystone species such as beavers, as we have at Idle Valley and using more natural approaches to reducing flood risks associated with climate change. By working with, rather than against nature, we can create more space for nature and continue to provide people with vital opportunities to connect with nature in their daily lives.
For further details about Besthorpe Nature Reserve or other wetland sites where you might spot egrets or enjoy the sight of birds on Autumn migration visit: www.nottinghamshirewildlife.org/nature-reserves
Nottinghamshire Wildlife Trust
Tel: 0115 958 8242
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www.nottinghamshirewildlife.org
Images:
Attenborough Nature Reserve, image courtesy of Richard Rogers.
Cattle egret, image courtesy of Mike Vickers.
Comma butterfly, image courtesy of Jaco Visser.
Comma caterpillar, image courtesy of Trevor Pendleton.
