Peter Contos, La Trobe University.

As an invertebrate ecologist, I spend a lot of time thinking about things that people often brush to one side. I mean this literally: my study species live in the leaf litter layer, the same layer that you’d rake into the green bin on a Sunday.

In that leaf litter layer, there is an incredible number of invertebrate species that all fulfil a pivotal role in breaking down and recycling nutrients into the soil. You really have to stop, slow down, and take your time observing what’s hiding beneath your feet. When you do you are rewarded with what is almost an endless diversity of forms and functions from large earthworms to tiny mites, springtails, and insect larvae. They may not be as flashy as pollinating insects, but they’re just as important.

If invertebrates are the ultimate underdogs, then leaf litter invertebrates are seriously under-estimated and under-valued. 

Often maligned and overlooked, it’s only recently that we’ve started learning about their shocking decline globally. This has thankfully triggered a reaction from the public and motivated researchers to think about ways to actively restore invertebrate communities. This is where my research comes in: my PhD project is focussed on rewilding litter-dwelling invertebrates to improve biodiversity and ecosystem function.

By “rewilding”, all I mean is that we’re trying to reintroduce invertebrates into areas where they struggle to populate themselves. We’re doing this on privately managed farms in central Victoria that have been partly revegetated. I think it’s fantastic that farmers have put aside part of their pasture for the sole purpose of biodiversity, and it’s always reassuring when a farmer stops you and asks how the invertebrates are responding to your experiment.

However, one of the issues with the way these farms have been revegetated is that the revegetation often exists as an isolated patch of habitat surrounded by invasive pastures. Think of an island in the middle of the ocean – the further out it is, the harder it’s going to be for animals on the mainland to colonise the island. Only the strongest dispersers will get there. It’s not a tough ask for a large bird to get there but a tiny insect without wings has much more limited options.

Our evidence suggests this is very much the case with our litter invertebrates. Many species seem to be struggling to disperse from surrounding remnant sites into new revegetated habitat. This has resulted in lower diversity of invertebrates on our farms and, therefore, reduced ecosystem functioning.

My project is giving these little invertebrates a helping hand by actively transplanting them from biologically rich remnant sites into the revegetation sites. We take whole samples of leaf litter from remnant sites containing hundreds of invertebrate species and thousands of individuals and dump this litter into the revegetation sites as our rewilding event. It’s as simple as that.

Litter transplants definitely lack the glitz and glamour of, say, a bilby reintroduction but transplanting leaf litter is a simple and effective way to reintroduce potentially hundreds of different invertebrate species to areas where they’re needed. What we are doing is essentially speeding up the restoration of communities such that they become more similar to the “pristine” remnant areas – this is the ultimate goal of ecological restoration.

It has been about four years since the first rewilding event, so we’ve started to look at the complex effect it has had in the revegetation sites. What we’ve found is that the number of beetle species has markedly increased in rewilding areas and this happened as early as 7 months after our first rewilding event.

Litter invertebrates are keystone drivers of leaf litter breakdown. So, if we’ve altered their diversity, has there been a parallel change in litter breakdown? We’ve measured this using bags of leaf litter left in the field for months and found that yes, rewilded communities are able to break down litter and recycle this back into the soil faster than before.

These results are really important for the cause of invertebrate conservation but they’re only the beginning. Projects like mine are relatively novel and it’ll be a while before we learn to develop the best way to restore entire invertebrate communities. I’m happy just to be playing my small part in promoting these under-appreciated animals.

Images: (Top) a species of huntsman we like to call the “lorax spider”; (Bottom) a millipede that typifies remnant sites.