Rewilding boosts plant diversity

Headline photo: Graeme Lyons. 

Overview

A vegetation survey in 2022 shows that the rewilding project at Wild Ken Hill has significantly boosted planted diversity in just 3 years. Specifically, the average number of different plants in sampled areas has roughly doubled between 2019 and 2022.

This is a hugely encouraging result. It shows the power of the rewilding approach and in particular the positive benefits of reinstating natural grazing at a landscape scale.

Project Manager Dom summarised: “There is a popular misconception that rewilding is simply about species reintroductions, afforestation, or bringing back specific species like beavers. But the truth couldn’t be more different at Wild Ken Hill. The very fabric of the ecosystem is being restored from the ground up in a science-based, nature-led, and low cost manner. The full suite of species will benefit, from plants and invertebrates to birds and mammals.”

The survey

You may remember that a baseline survey of the structure and composition of vegetation in the rewilding area was conducted in 2019. Phenomenal naturalist Graeme Lyons completed the survey, writing some rather brilliant blogs about his excursions around Wild Ken Hill. We wrote our own blog about it here, and the results of that 2019 work are also available here.

Ecological recording is technical, and this survey is bespoke for nature recovery projects like Wild Ken Hill, but we can try to summarise in lay terms how the survey works. About 100 evenly-spaced plots were created in the rewilding area in 2019. Each is a circle with about a 10 metre radius, creating an area of 300 m². In each plot, Graeme would record the structure and composition of the vegetation. Species-richness, nectar abundance and diversity, structural types, seedlings, saplings, canopy trees and dead wood were all counted, identified and measured.

The same vegetation survey was repeated by Graeme in the summer of 2022, albeit focusing only on plots that were formerly in arable farming, conservation margins and existing grassland (of which there were 57). In the woodland areas structural changes are expected to be slower and therefore require recording less frequently.

Using a super-accurate GPS system, Graeme was able to return to the exact plots, recording the structure and composition of the vegetation in the same way. Graeme then goes away and performs some magic at his desk to turn this information into usable data that can provide insights on biodiversity performance. If you’re keen to get into the detail, a full version of the 2022 vegetation survey is now available here.

This is the first time we have repeated a major ecological survey in the rewilding area since the baseline year of 2019. Of course a variety of research and monitoring has taken place in the meantime, but this is first repeated survey which can show meaningful changes over time.

Key Findings

The headline survey result is that the average number of plants in open parts of the rewilding area roughly doubled from 16.8 to 33.2, this being highly significant in a statistical sense. As we said, this is hugely encouraging. Within this average figure, there is of course plenty of variation though.

An important dimension is the broad habitat type prior to beginning the rewilding process. The biggest improvements were typically seen in plots located within fields themselves. In these plots, the average number of plants grew from around 7 to around 32! A massive and highly significant increase!

In plots that were formerly in conservation margins and headlands around fields (“edge” areas), or the few areas of former grassland, changes to the number of plant species were mixed in edge areas, the average number of plant species per plot went from 31.3 to 40.2, while in grassland areas it went from 27.7 to 29.8 (but these changes were not statistically significant).

One plot, located on particularly sandy soils in a previous arable setting, went from 4 to 48 species of plants! But of course, not all plots went up.  But others remained steady or slightly declined.  And not all plants necessarily spread. While the abundance of Common Cudweed, for example, rocketed upwards, the abundance of other plants with conservation status reduced – more on this important finding later.

Other results

The mean number of species with conservation status per plot rose significantly between 2019 and 2022. This was really a result of plants like Common Cudweed and Smooth Cat’s-ear spreading quite prolifically through the rewilding area, bringing up the average.

A total of 1,075 seedlings were recorded in 2022, as compared to 651 in 2019, showing how the natural regeneration of scrubby and tree species is also beginning to take place in the open plots, albeit slowly due to the natural grazing regime – more on this below. The most abundant seedlings were Ash, Pedunculate Oak, and Broom (in that order).

Graeme’s report also shows that the abundance and diversity of nectar sources rose significantly between 2019 and 2022. This should be great news for invertebrates going forward.

For those interested in those more detailed and granular statistics, the report is absolutely full of them, and as a reminder can be viewed here.

What it means for wildlife

It is perhaps trite to say that plants are fundamental to the ecosystems that they and a variety of other species inhabit. Along with a variety of other roles, plants provide the food and shelter for an array of insects and birds. So enriching the plant life at Wild Ken Hill is not only significant in itself, but should lead to knock-on benefits throughout the ecosystem.

Hetty, the Conservation Manager at Wild Ken Hill, described what these changes mean: “The results from the survey are very exciting for wildlife. For example, take Graeme’s work showing the increase in the variety and abundance of nectar sources. We know that increasing food resource for invertebrates like this will have positive knock-on effects right up the food chain, benefiting all manner of birds, bats, and more”.

Graeme Lyons, who produced the survey, also chimed in, saying; “This is kind of standardised and repeatable survey is important for generating meaningful data that can help to inform not only Wild Ken Hill but the rewilding movement as a whole. Nuance is key to this understanding, and this insight only comes from monitoring in such a detailed way. Those sandy fields at the south of the site that have had such a significant change are remarkable, to think they were just Sugar Beet and Spring Barley three years ago and now they are (in places) full of flowers, with Common Cudweed, Smooth Cat’s-ear and some Silver Hair-grass is fantastic. The planned pulsed grazing will improve the site even more and help maintain the existing grassland in good condition”.

Natural Grazing at Wild Ken Hill

Herein lies some interesting and topical nuance in subtle differences between rewilding approaches. Readers will likely be familiar with the differences, say, between formerly arable lowland Wild Ken Hill and an upland rewilding site like RSPB Haweswater in the Lake District.

Upland sites often benefit from reduced grazing intensity and may require tree planting to encourage the regeneration of native species. Lowland arable sites, conversely, often need natural grazing regimes but not planting due to the variety of existing vegetation.

However, it’s also important to recognise that within lowland sites, approaches to rewilding and in particular natural grazing must vary to create the biggest improvements in each site. For example, Wild Ken Hill benefits from a mixture of different soil types, many of which are free draining – factors which can lead to brilliant plant diversity. Indeed, plant diversity at Wild Ken Hill was incredibly strong, even before the rewilding process began.

As such, it was very important for the rewilding approach at Wild Ken Hill to use a natural grazing regime that encouraged plant diversity. We are not saying we have done this perfectly, and there are improvements to be made, but this was certainly the intention.

To do so, we introduced natural grazing relatively early in the project lifecycle – after just one year – to accelerate the change towards species-rich grassland. The results of this survey show that this has worked to a degree. One corollary of introducing grazing animals the rewilding system quite early, however, is that it will slow down (but not stop) the natural regeneration and proliferation of scrubby and woody species.

Other lowland rewilding projects may seek instead to introduce natural grazing later. For example, we know from Isabella Tree’s inspirational Wilding that giving the vegetation in Knepp’s southern block around five years free from grazing allowed it to “pulse”. Our understanding is that this supported a fast succession towards a scrubbier landscape. This landscape now supports the UK’s only growing population of Turtle Doves and an array of other nature success stories.

While our long-term vision at Wild Ken Hill is for scrub and wood pasture to emerge in areas currently very open, we did also want to exploit the floral diversity that our heterogenous and light soils could offer. Hence our slightly different approach to natural grazing.

The point is that there is no one size fits all approach to rewilding. Individual projects should baseline their own sites before putting back in place natural processes that they believe will generate the most biodiversity benefit. This will lead to varied and nuanced approaches being used across the UK.

Areas for improvement

The survey results show that the introduction of natural grazing into the rewilding area has assisted a rapid transition from arable farming to a grassland with growing species richness. While this has been effective for the past two or so years, it might not be the best way to go forward.

The survey does show, for example, that areas which already good levels of species richness have not benefited from the nature grazing regime to the same extent as the farmland. This includes some former conservation margins and small pockets of former grassland.

By doing the same thing, everywhere, all of the time, livestock can start to act as a homogenising force, rather than increasing diversity. Going forward, introducing pulsed grazing is likely to be a more effective tactic. That is, allowing for large parts of the site to be rested at any one time, bring a disturbance cycle into the mix.

In terms of rewilding, some would argue that this is actually more naturalistic than keeping grazing levels continuous in one (albeit relatively large) area, as the former emulates predator/prey relationships and seasonal migration.

Professor Alastair Driver, Director at Rewilding Britain, summed this up well: “We’re delighted to see this important report from the incomparable Graeme Lyons. Ensuring botanical diversity is one of the greatest ecological challenges facing rewilding projects in Britain – partly because our botanical baseline is often very low to start with, partly because we are missing most of the large native herbivores we once had and partly because we are still dealing with relatively small sites.

“We therefore have to find ways to balance the ‘hands-off’ principle of rewilding with the primary purpose, which is to restore natural processes and biodiversity at as large a scale as possible. These findings neatly confirm what many of us have suspected, that low level extensive grazing by proxies for those extinct species can bring good results, but that moving animals around to perhaps replicate the apex predator ‘fear factor’ in situations like this, can also be very important.”

The good news is that at Wild Ken Hill we are already looking at developing the ability to introduce pulsed grazing at some stage in 2023, including building better livestock handling facilities and using Nofence collars on the Red Poll Cattle, and creating alternative grazing sites around the rest of Wild Ken Hill, meaning we can move livestock off of the rewilding area for periods of time.

Summing it up

The diversity of plants in an average area has doubled in just three years, demonstrating the effectiveness of the rewilding approach for ecosystems. This is significant in itself, but will also provide knock-on benefits for insects, birds and other species over time. It is such an encouraging step on the long-term rewilding journey at Wild Ken Hill. The results show the importance of tailoring rewilding to individual sites. They contain a variety of learnings and implications for forthcoming management decisions at Wild Ken Hill.

We hope you enjoyed this more detailed blog. We look forward to keeping you abreast of other biodiversity success stories at Wild Ken Hill. If you’re interested to understand more about rewilding, our guided tour “Rewilding in Practice” is an excellent way to see what the word really means on the ground.  Do take a look – we hope to see you soon!