Rewilding minibeasts: How can we restore invertebrate and microbe communities?

Blog written by Peter Contos. Read the full article here.

(Photographer: Matthew Brun)

Ecological restoration is needed now more than ever in the face of an unprecedented, human-mediated extinction crisis. Our current efforts are massive and amount to billions of dollars invested each year to repair environments and restore flora and fauna communities. However, when you invest such large amounts of money there is an equally large pressure to demonstrate successful restoration, which prompts the question: are we getting the most bang for our buck?

Despite massive investments of resources, many restoration projects often fail to fully recover biodiversity and function to pre-disturbance levels. The root cause of this is likely highly contextual. However, the inability of dispersal-constrained organisms to move to and recolonise newly restored habitat may lead to lower-than-expected levels of biodiversity and function. Invertebrates and microbes (or “minibeasts”) may be key players in this phenomenon as they both make up the unseen bulk of biodiversity and are often dispersal constrained. Solving this issue may be as simple as actively reintroducing or “rewilding” dispersal-constrained minibeasts during restoration. Yet, this is rarely considered during contemporary restoration and rewilding projects.

We wanted to challenge the current approach to restoration and rewilding and explore why minibeasts are so often undervalued for their restoration potential. So, we reviewed the current state of minibeast rewilding projects and looked at how they have been implemented during restoration to improve biodiversity, function, and the likelihood of better ecosystem recovery. As expected, we found very little attention has so far been paid to minibeasts during rewilding projects. In the related field of reintroduction biology, invertebrates make up as little as 3% of projects despite their roughly 95% contribution to species diversity. We found that most rewilding projects seem to centre on single species reintroductions of earthworms to restore soil processes, and Arbuscular Mycorrhizal Fungi to improve plant health.

Litter invertebrates are rarely considered for rewilding projects despite their immense importance for biodiversity and efficient nutrient cycling rates (Photographer: Louise Menz)

We argue that there are significant missed opportunities within these current projects that are only sometimes realised. For instance, minibeasts are miniscule and easily manipulated, meaning whole communities can potentially be rewilded in a single instance. This is a quality unique to minibeast rewilding and skips the slow species-by-species reintroductions needed to build communities in traditional (vertebrate-focussed) rewilding projects. In our review, we found 21 examples of “whole-of-community” minibeast rewilding during restoration. Most of these centred on soil inoculation studies, where soil from remnant habitat is moved into restoration sites. However, even though these projects have tried to rewild the whole soil community, only 29% and 35% measured changes in invertebrate and microbial communities post-rewilding respectively. This highlights that even within the limited examples of minibeast rewilding, a smaller percentage of those actually record the effect on communities.

So, how can we extend and improve current projects? Well for one, we can start to think about how we can better apply minibeast rewilding projects. Soil inoculation, although in its infancy, is proving to be an incredibly powerful method for both restoring minibeast communities and improving ecosystem function. Yet, minibeasts are hyper diverse and drive a range of functions, meaning there may be many more applications outside of soil inoculation. We wanted to spur greater empirical testing of whole-of-community rewilding, so we provided case studies that land managers can use during restoration to improve ecosystem recovery.

One of our case studies describes an as-yet untested way to improve the critical function of litter decomposition. Litter-dwelling detritivore minibeasts are critical for efficient rates of nutrient cycling. They break-down leaf litter into a form that is usable for plants. They are however often dispersal constrained and so may struggle to move from remnant sites into restoration sites, potentially limiting diversity and the speed of litter breakdown during restoration. In our article we describe how this relatively simple project would look: litter rewilding would involve moving litter, with whole minibeast communities in situ, from biologically rich remnant sites into restoration sites. This may rapidly increase biodiversity and introduce functionally important species, thereby improving the efficiency of litter breakdown during restoration.

Leaf litter taken from remnant patches and moved across dispersal barriers may introduce a multitude of dispersal-constrained species.

Invertebrate conservation is currently in a critical moment – knowledge of the alarming global declines of invertebrate communities is starting to seep into mainstream discussions. We need every tool in our arsenal to stem the so-called “Invertebrate Armageddon”. Some of the ideas proposed in our review may provide additional options for invertebrate conservation. For instance, whole-of-community soil rewilding has been shown to improve the diversity and density of mites and springtails, the abundance of wetland macroinvertebrates, soil nematode abundance, and soil macrofauna abundance. By extending the use of whole-of-community rewilding to other elements of the community (e.g., litter communities), restorationists will have a new tool in the fight against invertebrate declines.

Our review is the first to describe the state-of-field of invertebrate and microbial rewilding projects. The overarching aim of our article was to open the discussion around how we have approached ecological restoration so far. Restorationists are currently overlooking two groups that make up the bulk of biodiversity, which brings into question whether most projects are failing to reach their eventual goal: the reinstatement of biodiversity and function in its entirety. We hope that by reading our discussion, ecologists form a greater appreciation for the rewilding potential of minibeasts and start to think about how they can better apply minibeasts to restore ecosystems.

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