In the final blog in our mini-series Malcolm Ausden, a Principal Ecologist for RSPB, looks at how we create and manage new habitat for wildlife under a changing climate. This topic is one of the many issues covered in the RSPB's new report on the impacts of climate change on wildlife.
Changes in climate add an additional layer of complexity to how we design and manage our nature reserves. How do we decide what’s best to do now, when the climate and species’ distributions are likely to be quite different in the future? And how is the climate likely to change anyway?
Despite the uncertainties over how the climate might change, there is sufficient consensus on its expected direction of travel, to help inform what we need to do now.
When deciding actions to try and lessen the overall impacts of climate change on wildlife, it is useful to distinguish between two types of timescales. First, there are measures which we can adapt on short timescales as weather conditions change. For example, changes in climate will affect plant growth, and thereby the number of cattle that we need to graze a wet grassland to provide suitable sward conditions for breeding waders. But we don’t have to plan cattle numbers several decades in advance. Instead, we can adjust our grazing levels on a short timescale in response to growth conditions during that particular year. We just need to be adaptable, and to make informed decisions based on continually monitoring and reviewing of our actions and their impacts.
In contrast, when we are re-creating good wildlife habitat, we want to design this habitat so it continues to provide suitable conditions under a wide range of future climates. This requires taking into account how the climate, and species’ distributions, are expected to change. There are two main situations where we are doing this. The first is in the design of new coastal wetlands, to help offset expected future losses of these due to rising sea levels and increased coastal erosion (as well as to help offset historical losses through land claim). The second is in the hydrological design of our freshwater wetlands, in which we take account of expected future changes in water availability.
We are designing out new coastal wetlands so that they should continue to provide valuable habitat for wildlife under a wide range of future sea levels. A good example of this is the innovative design of the RSPB’s Wallasea Island Wild Coast Project in Essex. Innovative features at Wallasea include the creation of ‘sea level rise adaptation zones’ - gently sloping areas of land designed to maintain rare transitions between high salt marsh and non-tidal grassland under a range of future sea levels. There is an article describing the design and construction of Wallasea in the August edition of British Wildlife.
A good example of a freshwater wetland designed to help cope with expected future changes in water availability is Frampton Marsh RSPB reserve in Lincolnshire. Here, as in the rest of southern and eastern England, changes in climate are expected to reduce water availability in late spring and summer, while periods of heavy rain and drought are also expected to become more common. At Frampton, we collect water in winter (when there is plenty of it) and store it in two reservoirs, so we can use this to top up water levels on the rest of the reserve in late spring and summer. We have also designed the wetland so that different sections of it can be periodically dried out and re-flooded. This not only provides valuable, newly flooded habitat for birds, but also means that in dry years, we have the option of only keeping some areas wet, while in wetter years we keep a larger proportion of the site wet.
We have also been liaising with colleagues on the Continent to increase our understanding of the requirements of birds that might colonise (or are just about colonising) the UK, due to changes in climate and recovery from past declines. Examples of these include Spoonbill and Black-winged Stilt. We have been building the requirements of these and other potential colonists into the design of our wetlands for the future.
The fourth blog in our series comes from the British Trust for Ornithology's Science Director, James Pearce-Higgins. You can read far more on any of the topics in this mini-series on our new report on the impacts of climate change on wildlife, released one week ago.
Managing species in the face of climate change
In the UK, our peatlands are one of the environments most threatened by climate change. Active peatland depends upon a high water table to encourage the growth of Sphagnum mosses, and other vegetation, which through time, decompose and are slowly converted into peat, locking away the carbon they contain. In most upland areas, these peatlands are rain-fed, and therefore they tend to be most strongly associated with western and northern Britain.
This means that the extensive areas of blanket peatland in the UK are not only vital to protect in order to reduce greenhouse gas emissions, but that they will be vulnerable to changes in precipitation and increases in temperature caused by climate change, which can reduce water tables. The species which occur on them may also threatened by climate change in the same way. For example, the golden plover, like a number of other bird species, associates strongly with blanket peatland areas, where a flush of invertebrates in spring provides abundant food for its young. The most important of these are craneflies, whose larvae are vulnerable to desiccation when the peat dries-up in hot summer weather, providing a strong link between soil moisture, insect abundance and golden plover abundance. As a result, the golden plover population in the Peak District may be vulnerable to extinction under a high climate change scenario by the end of this century.
We are not without tools to combat this threat. Through appropriate management, it may be possible to counteract the impacts of climate change. Much of our peatlands are in poor condition as a result of historical drainage and erosion. By blocking these drainage channels, we can raise water tables, improving the condition of the vegetation, and increasing cranefly abundance by up to five times, increasing the resilience of populations of peatland birds, such as the golden plover, to climate change.
Alternatively, management may be able to compensate for the impacts of climate change by improving a species’ population status without directly addressing the climate-related mechanism causing decline. In the example of golden plovers, which can be susceptible to its eggs and young being predated by generalist predators such as corvids and foxes, this could be through management to reduce predation.
Although in the face of climate change, the long-term persistence of many of our upland birds may seem unlikely, it appears there is much that conservationists can do to slow or prevent such declines occurring. Recent evidence that populations of northern species threatened by climate change have persisted longer in protected areas likely to be managed favourably for them, than in the wider countryside, supports this. Looking to the future, our ability to replicate this model elsewhere will depend upon understanding the mechanisms driving each population’s response to climate change, and maintaining the resources to support such active intervention.
Today, Dr Richard Bradbury, the RSPB's Head of Environmental Research, explains how climate change is already forcing wildlife to move. You can read much more about this in our new report on the impacts of climate change on wildlife, that we published just this week.
Things aren’t like they used to be....
When I was a kid, looking at my first field guides, I got used to the idea that species lived in particular habitats and in particular places, marked in a bright colour on a range map. For instance, I got used to the idea that there was a set of native British breeding birds, some of which were common and widespread, some less so. Some, like the Dartford warbler, were specialists of the lowland heaths of southern England, while others, like the dotterel and ptarmigan, were specialists of the montane plateaus of northern Scotland. And of course there was that exciting list of rare visitors, like little egret, that I might just see one day – if I was very lucky.
As I’ve grown older, this fixed view of the world has changed a lot. Species that were common when I was young, from the turtle dove to the tree sparrow to the garden tiger moth, are now much less abundant. Various factors, including changes in agriculture, have driven these declines. Other species, like red kite and marsh harrier, have increased in numbers thanks to conservation efforts.
But now, climate change is also having a dramatic effect on the suite of species which are familiar in any given part of the British Isles. From the south coast, since the 1970s, Dartford warblers have charged north to mid Wales, the English midlands and East Anglia. Having lived about as far north as north Wales prior to 1982, the comma butterfly has now spread as far as Aberdeen. From grasshoppers to spiders to fish – these northwards shifts are being shown right across our wildlife. We’re very confident these northwards advances are in response to the warming British climate. On the other hand, our dotterel population has halved and shrunk in range in the last few decades – maybe this is signs of a climate-driven retreat? And some less mobile warmth-loving southern species, like sand lizard, haven’t moved north as the climate has ameliorated for them – because their habitat is too fragmented.
Northwards shifts in range are exactly what we’d expect under climate change. We’d also expect species to move uphill. And we see this too. Mountain ringlets, perhaps our only truly montane species of butterfly, appear to be losing their lowest altitude colonies. Dartford warblers (that lowland heathland specialist) are now breeding over 400m up the hill on Exmoor.
Even more spectacularly, a host of species are expanding their ranges north and colonising the British Isles for the first time. From small red-eyed damselflies to tree bumblebees to wetland birds. That rarity of my childhood, the little egret, is now a common sight in the southern half of Britain.
So what does this all mean? Well, at a personal level, I find it both thrilling and sobering. I’m wondering when great white egrets will first breed on my local reserve! But, at the same time, I wonder how long I’ll be able to go up to the Scottish highlands to see dotterel. At a professional level, the evidence is clear that climate change is not some far-off threat to our wildlife – it’s here now, and we need to start adapting – to help less mobile southern species move north, and to try to help northern species to hang on. And that will have to include some thinking about when we consider a species to be ‘native’ – with the protection that can lead to. This isn’t an easy thing to decide when species are moving themselves in response to climate change and also being moved around the globe by us, sometimes causing problems when they arrive.