Understanding climate impacts and then doing something about it - some lessons from the bittern success story

One of the main messages from yesterday’s International Panel on Climate Change report (here) is that a changing climate is already having an impact on wildlife and things could get a lot worse.

Perhaps the starkest sign of climate change in the natural world is the great one-way migration polewards of species attempting to track their preferred climates. In Southern Britain, the distribution of species across a range of taxa is shifting an extraordinary five metres northwards every day. Since 1970, the Comma butterfly, for example, has expanded out of the South and the Midlands and can now be found across Northern England and in Scotland. Many species are crossing the Channel in their efforts to adapt to our changing climate. Our Ham Wall reserve appears to have become a particularly attractive welcoming pad for potential new colonisers from the south such as great white egrets, little bittern and glossy ibis.

Understanding how species distributions or their habitats may change as a result of climate change and then planning to do something about it, is a key feature of our practical conservation work for sites and species. 

For example, we plan the management of our reserves on a five-yearly cycle.  When it is time to review the management of a reserve the site manager brings together a team, including specialists in ecology, visitor experience and estate management.  Often the conservation officer from the statutory conservation body also attends.  The team create a vision of what we want the site to look like in 25 years time.  They look at how the changing climate and other factors are likely to affect the species and habitats at the reserve and also the way in which we are able to manage the reserve.  Using this information, they create objectives for managing the site over the next five years.  Recognising that we need to manage our sites adaptively, we review how well our management is performing against objectives every year and making changes where they are needed. 

We apply a similar approach when thinking about recovery plans for threatened species and habitats.  For example, we have over the past 20 years prepared  for more severe tidal flooding which are expected to damage and alter many of our coastal wetlands. This is a particular issue for the UK’s freshwater reedbed and its associated species – especially bitterns – because many of the few large (> ca 100 ha) freshwater reedbeds in the country are at risk from coastal flooding.

By Andy Hay, rspb-images.com

This long-term threat to our coastal wetlands prompted a strategy of creating and restoring freshwater reedbeds away from vulnerable coastal areas, to compensate for the expected eventual loss of coastal freshwater reedbeds. Driven by the RSPB and Natural England and by supported by EC LIFE-Nature funding, this has proved spectacularly successful, with an increasing proportion of UK booming bitterns now in reedbeds which are at no or low risk of coastal flooding (see graph below). This programme of reedbed creation is also facilitating large-scale range expansion of additional species such as the ones now appearing at Ham Wall.

Numbers of booming bitterns at RSPB reserves which are at different risks of coastal flooding. Flood risk is taken from the Environment Agency’s interactive flood risk map.

Other measures have also been put in place to reduce the impact of high sea levels at sites threatened by coastal flooding. Sea defences have recently been improved at Minsmere and Titchwell Marsh. The new sea walls at Titchwell were overtopped during the storm surge, but did not breach like many other sea walls along on the North Norfolk Coast. At Mid Yare, new sluices and a watercourse diversion have allowed saline water to be evacuated more quickly from the site. At Read’s Island, pipes had been installed into its estuary wall, to reduce the pressure on this wall from such an event. From a distance, it appears that this wall has held (although it has not yet been possible to visit the island). However, alternative sites are still not in place for the avocet population at Read’s Island, and need to be secured as a priority.

I end with a more sobering thought.

Yesterday's IPCC report is a timely reminder that nature conservation in a changing climate is going to get ever more challenging.  Even with great planning there will be limits to what nature will be able to cope with. Already, the global climate we have created is unlike anything seen for 800,000 years, over which time many of the plant and animal communities that we are familiar with have formed. That’s why limiting climate change by cutting our emissions is now as much part of modern nature conservation as creating wetlands and recovering threatened species.

This week we will be posting a series of case studies on the Climate Change blog (here) how climate change is already affecting the natural world in the here in the UK, and how the RSPB Centre for Conservation Science (here) is investigating this threat.  I shall continue to focus on the practical steps we are taking on our nature reserves.