Securing Biodiversity in Breckland - European Commission

Biodiversity Implications of the Changing Breckland ClimateBreckland has become wetter in autumn, spring and especially in winter with an increase in thefrequency of extreme rainfall events in all seasons. Breckland temperatures have become lesscontinental, with much milder winters, milder nights in spring and summer, and fewer frosts. Thesechanges are predicted to continue under current climate change scenarios. Note that the magnitudeof change in temperature may have been under-estimated in our analysis, due to the relocation ofthe Santon weather station from Grimes Graves to Santon Downham – making our test conservative.These changes are likely to have profound consequences for ecological processes, for vegetation, andfor species. These can only be considered qualitatively and with a large degree of uncertainty.Possible effects may include: Wetter winters may favour leaching of mineralisable nitrogen down soil profiles, making theuse of soil disturbance treatments to reduce soil fertility more effective. Greater winter ground-water recharge may occur, with positive benefits for fen and pingo(fluctuating waterbodies) systems. However, it is recommended that ground water scenariosbe explored by models that combine temperature and precipitation in equations for potentialevapo-transpiration. Milder and wetter winters are likely to result in greater growth of perennial grasses that werepreviously kept in check by low winter temperatures and frost. Anecdotal evidence suggeststhis is already occurring within Thetford Forest. Greater grass growth would result in morerapid sward closure and encroachment onto bare ground to the detriment of speciesrequiring bare sand or exposed mineral soil. This may be mitigated by greater use of soildisturbance treatments, and adjustments in grazing regimes to remove excess biomass.Current climate predictions indicate that summers will be warmer and drier; if summerdroughting increases significantly, this may mitigate some of the effects of the milder, wetterwinters. Many of the Breckland speciality and coastal species are more widely distributed incontinental steppe or Mediterranean ecosystems. These are often stress tolerant butvulnerable to competition, or to pathogens that can be active in damper or more temperateconditions. Thus wetter autumn, winter and spring soil conditions may be detrimental toseeds, aestivating plants or soil dwelling insect larvae. For example, beetle larvae adapted toxeric conditions may have less resistance to fungal pathogens that can be important inpopulation dynamics (Holland 2002).In addition, frost can reduce the vigour of competitors, while also providing small scale localsoil disturbance in frost heave; both processes will be reduced.It will be hard to disentangle responses to changing weather from other changes (land-use, habitatextent), particularly for species whose ecology, distribution, and past and current status are poorlyknown.Recommendation: Ground water scenarios should be explored by models that combine temperature andprecipitation in equations for potential evapo-transpiration. Attempt to mitigate increased vegetation productivity from milder and wetter winters bygreater use of soil disturbance transpiration and adjustments in grazing regimes to removeexcess biomass.97