Martin Gaywood and Angus Tree Scottish Natural Heritage

Transcription

1 Scottish Could Natural beavers Heritage have a role in river restoration? Martin Gaywood and Angus Tree Scottish Natural Heritage

2 What we re going to talk about Some background The effects beavers can have on freshwater systems Some thoughts on where next, and possible implications for river restoration

3 Background

4 Beavers are (just about) back 24 th November 2016 Announcement by Roseanna Cunningham, SG Cabinet Secretary minded to allow beavers to remain in Scotland A historic decision the first formal reintroduction of a mammal species anywhere in GB Beavers are a game-changer back in the Scottish (and English/Welsh?) countryside

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6 Requested by the Scottish Government Designed to support Scottish Ministers in making a decision on the future of beavers in Scotland Collation of over 20 years of work Published June pp

7 The effects beavers can have on freshwater systems

8 Beaver ecology basics Live in territorial, family groups Herbivores - herbaceous + woody species Habitat - standing or slow-moving freshwater next to riparian broadleaf woodland They can modify their landscape

9 Beavers as natural agents of change Allogenic ecosystem engineers Engineering activity creates new habitat and alters the distribution and abundance of organisms in an area

10 The effects of beaver activity on hydrology Water accumulates upstream of leaky dams During periods of high precipitation, dams may slow the passage of water and lower peak flow Where dams extend onto floodplains, significant reservoirs of water may be available to maintain flow during periods of low precipitation

11 The effects of beaver activity on geomorphology Changes to the transport and distribution of sediment, woody material and other organic matter Altered patterns of erosion and deposition, e.g. material will settle upstream of dams Gorshkov, Sumka River, Tatarstan 4,250 t sediment stopped by cascade of three beaver dams 53% reduction (0.46 to 0.26 g/l) in suspended solids 1 Gorshkov D (2003) Is it possible to use beaver building activity to reduce lake sedimentation? Lutra 46(2):

12 The effects of beaver activity on habitat and species Together, the effects of beaver activity on hydrology and geomorphology can lead to the alteration of existing habitat and the creation of new The lack of habitat diversity in a modified watercourse may be transformed by beaver activity and a mosaic of different habitat types created Existing habitat may be improved, e.g. a reduction in the deposition of fines downstream of dams could improve spawning habitat

13 Extract from the Blaeu Atlas of Scotland 1654 reproduced with the permission of the National Library of Scotland Scotland has changed Crown copyright and database rights [2017] Ordnance Survey

14 Scotland has changed Land management and pressures on the environment have changed over the last years Most contemporary research undertaken in other countries

15 Some thoughts on where next, and possible implications for river restoration

16 We can summarise Beavers will have an impact, sometimes significant, on the freshwater environment Some of these impacts might be neutral or detrimental e.g. salmonid migration, localised siltation of river beds, riparian woodland regeneration But some might be positive e.g. salmonid spawning areas, decrease in siltation of river beds, riparian woodland restoration ( beaver lever effect) river restoration role? Challenge is how to reduce the negatives and promote the positives

17 Potential core beaver woodland: Mainland Scotland Total of 106,000 ha of potential core beaver woodland Stringer, Blake & Gaywood (2015). Scottish Natural Heritage Commissioned Report No. 875

18 A role in Natural Flood Management? Increasing interest, including in media NFM involves runoff reduction (e.g. non-floodplain wetlands), floodplain storage (e.g. riparian woodland) and sediment management (e.g. sediment traps) Beaver activities parallel some of these techniques Significance will vary in terms of time + space, beaver systems are dynamic Beavers can t be told where to go and what to do! (use of enclosures?)

19 Research needs Many potential topics, some priorities relating to river restoration might include: Salmonid/fish-beaver interaction (ongoing - Rob Needham, Univ Southampton) Deer-beaver interaction and impact on woodland regeneration Experimental studies looking at potential role of beavers in NFM, and development of predictive models Prediction of damming locations and impact

20 Tweed catchment (Scotland) 90% of river sections are less likely to be dammed by beavers Stringer, Blake & Gaywood (2015). Scottish Natural Heritage Commissioned Report No. 875

21 Next steps During 2017 the priorities in Scotland are: Habitats Regulations Appraisal (HRA) Strategic Environment Assessment (SEA) Management framework (e.g. licensing) New surveys of Tayside and Knapdale populations Knapdale population reinforcement all leading to European Protected Species status Beyond 2017 Opportunity to develop wider strategic approach to beaver management in Scotland. Many complex biological factors, legal and socio-economic considerations. Opportunities for river restoration are there, but need to fit within wider strategy

22 Next steps The longer term - We now all have to recognise there is a new river engineer on the scene which will become increasingly influential on freshwater systems The challenge for river restorers - Time to start thinking how we learn to live with beavers, and make use of the opportunities they could bring

23 Thank you