Two beavers this morning at 5:00, one noisily chewing near the hole and the other swimming across. When it was still not quite light he or she plunked down toward the edge of the water and munched something with their back turned to the intrusive humans. We are on day 1 of “Project habituation” where we are trying to get the beavers acclimatized to us by repetition. I’ll let you know how it goes.
The only thing I was able to capture in with enough light was this feral cat making his own particular use of the beaver dam. It makes you think about how many species were affected when the beavers left, not just fish and ducks, but raccoons and deer. Beavers and their dams make such a difference that I’m sure many creatures come to rely on them.
One idea that Jeanette Johnson suggested at the meeting was scrabble tile earrings, which I of course had to try right away. I amused myself a great deal with these.
Hmmm do you think an etsy shop is in our future?
Very nice article from our friends in Devon, England that several folks sent my way. It deserves our only slightly divided attention. It doesn’t list the author, but its featured in the “rewildling britain” magazine.
Devon beavers are officially working their magic
As an ecologist, it’s clear to see how the beavers have had a huge impact within the enclosure. Habitat variety and structure are the first things that have changed – wet areas, ponds, deadwood, open grassland, scrub and trees and areas of sphagnum. Visually, there also seems to have been overall improvement in biodiversity.
But not everyone is an ecologist and sometimes we take it for granted that everyone sees what we do. Others may just see an electric fence, or a flooded area, or not really see it at all. So how can we influence political and economic decisions if we can’t relay this message to those who don’t appreciate or see nature and wildlife in the same way? How can we say for sure that biodiversity has been improved? Based on our experience, we would expect this to be the case, but in what way has change occurred? And how does this relate to other disciplines such as hydrology?
Beavers and biodiversity
We picked the most relevant indicator groups related to change associated with the beavers: bryophytes, bats and aquatic invertebrates
Ecosulis, driven by its shared vision of rewilding Britain, uses a Biodiversity Quality Calculator, developed by Dr Alan Feest, which measures change in biodiversity quality.
The bespoke calculator has been used in many ways to measure change as a result of management prescriptions and to gauge the effectiveness of biodiversity off-setting schemes. More recently, it was used to measure the change in biodiversity quality, using a range of indices, as a result of the beaver reintroduction at the experimental site in Devon.
Particular focus was given to finding out if the beavers could help maintain the open grasslands in the face of encroaching scrub species. This could allow us to see how biodiversity changes over time and could also be linked to other environmental changes, such as nitrogen or hydrology. This could then also be used to influence decisions on whether reintroductions should be undertaken on a wider scale or if management plans and prescriptions should be modified.
To do this we picked what we agreed to be the most relevant indicator groups related to change associated with the beavers: bryophytes, bats and aquatic invertebrates. One of the key benefits of the calculator is that historical as well as current data can be analysed, allowing for trends to be determined. We measured the changes in biodiversity quality between 2012 (one year after beaver introduction) and 2015 data collected by Ecosulis for bats and bryophytes (invertebrate data yet to be assessed). The data revealed some very interesting trends:
Bats
- + Increase in species richness
- + Increase in species evenness, indicating less dominance of common species
- – Decrease in species dominance
- + Increase in species rarity scores on the site, including rare grey long-eared and barbastelle bats
- + Increase in biomass, indicating an increase in invertebrate prey species on the site (and number of bats)
Bryophytes
- + Increase in species richness
- + Increase in species evenness, indicating less dominance of common species
- – Decrease in species dominance
- + Increase in biomass
- + Increase in nitrogen intolerant species (indicating lower nitrogen levels)
- + Increase in species associated with well-lit areas, and species associated with acidic soils
Invertebrates
- + Increase in species richness
- + Increase in species evenness
- – Decrease in species dominance of any one species
- + Increase in population density
- – Slight decrease in species rarity\
Rewilding – right here, right now
After an absence of 400 years, beavers are back in England and, within a few short years, are having an amazing effect
The scale and direction of the changes have been compelling. By taking a relatively simple, cost-effective and standardised approach to collecting biological records, a clear picture of biodiversity change has been recorded at the Okehampton site. The increase in indices such as biomass and species rarity reveals that habitat structure and the carrying capacity of the site have increased. A rise in biomass for bats indicates higher levels of invertebrate prey, which in turn benefits other species including birds.
The beaver have turned what was an area of dense scrub and simple channel into a mosaic of scrub, pools, dead wood, banks, culm grassland and habitat piles. After an absence of 400 years, beavers are back in England and, within a few short years, are having an amazing effect. Associated species are now diversifying and thriving, instead of declining – this is rewilding in action!
The full results are due to be published in the next Devon wildlife Trust Beaver Project update.
Beavers build nitrogen sinks
One unexpected consequence of the beaver was a potential reduction of nitrogen levels at the site, as indicated by the bryophyte assemblage recorded. By linking bryophytes with their nitrogen sensitivity we discovered that our data supports recent research that indicates beavers produce nitrogen sinks (Geographical. October 2015). This could be a handy additional tool in the argument favouring the reintroducing of beaver to Britain.
Clearly one of the fundamental principles of rewilding projects is that there is no ultimate destination. Rewilding is a journey and one that is to be shared both by people and wildlife. Like any journey, it makes sense to have a reference point to determine whether you’re heading in the right direction and are not back in the same place you started.
Our assessment measures the changes in biodiversity quality without the added value judgement of one species being more important than another. Instead, it tells you whether you have a dominance of any particular species, if you’ve recorded all the expected species present, what the spread and biomass of the species are and how this can be interpolated against the expected outcomes.
Once this quantitative assessment has been made, it can be incorporated into biodiversity and rewilding decision-making related to issues such as the location of rewilding projects, appropriate management regimes and the effects of externalities.
The next steps for the method are to help inform the debate regarding the decision to reintroduce beavers more widely back to Britain. We can also consider if this method might be applicable to other potential reintroductions such as those for pine martens or even lynx.
How’s that for a thorough recap of beaver benefits? Honestly I almost hope the United Kingdom never approves beaver reintroduction because it make for such fantastic efforts by the media to convince them – which benefit everyone! Go read the whole fabulous article, and share it with your friends or nonbelievers.
The city of Vallejo had such success with their Nature celebration last year for the anniversary of the State parks that they are working with USFS and FWS to do it again, specifically celebrating”Wild in the City”. Steve Dunsky has already asked me to give a Martinez Beaver intro and yesterday the project put out the plea for corporate sponsors. Uh oh. Check out their photo for the ‘Beaver sponsors’.
You would think that a team of scientists would know better than this, but you’d be wrong. Because I was three feet away from Dr. Michael Pollock of NOAA fisheries when he proudly displayed a photo of a nutria in is beaver talk. I of course wrote them they might want to make a correction, and supposedly they will. In the mean time their mass email asked us to share it on social media and I see no reason not to oblige.
