Those of us who work within the various countryside sectors will know that we don’t know everything when it comes to successful conservation, particularly with species reintroductions; everything is a learning process. And they will understand, or at least be aware of, the need to not only conserve our habitats but to ensure that said habitats are well connected throughout the landscape.
What is the use of having a beautiful replanted woodland or newly created pond if very few species can actually get there? Why reintroduce a species population to an area where it cannot interact with other populations of the same species?
A good example of evidence that thoughtful planning and habitat connectivity on a local and landscape scale is beneficial comes from a tale of reintroductions of the hazel dormouse. The People’s Trust for Endangered Species (PTES) carried out its first re-introduction of this iconic species in 1993 as part of Natural England’s Species Recovery programme and has since carried out an additional 25 reintroductions. The aim of these introductions is to restore dormice to areas of England from which they have been lost and where natural re-colonisation is unlikely.
It has not been plain sailing all the way however, and lessons have been learned.
The original reintroduction sites were selected independently of one another, usually in counties where dormice were once present but had since become extinct. While dormice have been shown to cross distances of up to 500m across open farmland and male dormice have been observed moving over 300m in a single night, adult dormice are generally sedentary and have permanent home ranges. Dispersing juveniles will travel, on average, between 127m and 363m from the natal site. Often these early reintroduction sites were kilometres apart and not all had connectivity to other areas of suitable habitat. So while the distribution of dormice increased, the stability and long-term viability of the populations released was questionable.
In a Natural England review into the reintroduction programme (2012), it noted there were between three and five populations failing to survive in the long term and others failing to expand into nearby habitat. Of the latter, one such population is the first reintroduction site at Brampton Wood, Cambridgeshire, in 1993. The population still exists but there is no evidence to date of dispersal into the surrounding environment; the population remains centred within the woodland, moving around depending on where the most suitable habitat is as a result of recent woodland management. And if you have a look at the map below (the woodland shouldn’t be hard to miss), you can perhaps see why…
After reviewing methodologies and looking back on data and success rates, a new strategy for reintroductions was developed; change the aim from one of expansion to consolidation so that viable metapopulations can be established. The most recent reintroductions have aimed to do just that, with three reintroduced populations released in Nottinghamshire during 2013, 2014, and 2015, living near one another and forming a healthier, genetically variable population with a much higher chance of long-term survival. And the information to date, early as it is, is encouraging, as efforts have been made to connect the three separate release sites with suitable habitat.
So a big lesson is to be learned from this example – when managing habitats for wildlife and carrying out species-specific conservation, habitat and population connectivity on a local and landscape scale is the key.
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