Rewilding with mini-beasts for biodiversity and ecosystem function.

HSF19037 | Amount: $87,000 | Project Leader: H Gibb | Project Period: Jul ’19 – Jul ‘22

A project undertaken at Latrobe University, and supervised by A/Prof Heloise Gibb.

Human damage to ecosystems through land-clearing or agricultural intensification causes a loss of biodiversity and a decline in ecological function. Increasing recognition of this loss has led to efforts to ameliorate damage by restoring ecosystems. Ecological restoration usually focuses on actively returning vegetation to degraded land through replanting of the overstorey (revegetation). More recently, the reintroduction of vertebrates (rewilding) has also been recognised as critical to the restoration of ecosystem function. However, invertebrates and microbes (“minibeasts”) are largely ignored in restoration attempts.

Fig. 1 Native isopods from the family Armadillidae

This is problematic because these species make up the vast majority of biodiversity and perform important ecosystem functions such as decomposition and nutrient cycling. In this project, we aimed to test the efficacy of methods to rapidly restore biodiversity of “minibeasts” to areas of farmland that have been revegetated, but continue to have depauperate assemblages of invertebrates and microbes. Knowledge of invertebrates and microbes is poor relative to knowledge of plants and vertebrates, making it difficult to produce a list of species we believe should be restored. We therefore opted to use entire communities of organisms associated with leaf litter and soil, which could be easily collected and transplanted from undisturbed remnant sites to revegetation.

This might also have the benefit of keeping interactions among species that are dependent on one-another intact, even if our knowledge of those interactions is sparse. We conducted transplants at six revegetation sites, each of which was paired with an undisturbed remnant (the source of the transplant) and a revegetation site that we left untreated, as a control. We monitored litter invertebrates and microbes and measured leaf litter decomposition over time.

Fig. 2 A native millipede from the family Paradoxosomatidae

Our experiment revealed some key lessons. First, some, but not all species will be restored using this approach. We found that the main group to benefit from the litter transplants was beetles: transplants increased the species richness of beetles in revegetation sites to a similar level to what is found in remnant sites. Beetles are relatively robust organisms, with high desiccation tolerance, due to their thick cuticle and sclerotised forewings (elytra) that protect their abdomen and hind wings. These characteristics may have allowed them to tolerate the transplant and harsher conditions in the revegetation sites better than other species. Introducing new species to revegetated farmland increases the area of habitat available to those species, increasing their chances of persistence across the landscape.

Second, ecosystem functions can be improved, even if not all species become established. Even though many of the transplanted species did not persist in the revegetation sites, the experimental transplants increased litter decomposition rates, suggesting that enough species persisted to alter ecosystem function. Increased litter decomposition indicates faster cycling of nutrients back into the soil, making them more readily available for plants and generally driving productivity of ecosystems, so this is a clear benefit.

Trilobite cockroaches
Isopod I

Third, species interactions can be enhanced by litter transplants. We found that the microbiome of a common native beetle, the honey brown beetle, Ecnolagria grandis, increased in size following transplants, whereas that of the introduced Portuguese millipede, Ommatoiulus moreleti, remained unchanged. This suggests, that for some species, the transplant experiment has led to new interactions with microbes, although it is not yet clear whether this is beneficial.

The idea of “rewilding with minibeasts” is new and this was the first effort to establish its efficacy. The experiments revealed that the potential of this approach to effectively restore some groups of organisms, ecosystem functions and even species interactions is high. However, further research is needed to refine approaches to improve our ability to use whole of community transplant methods to maximise biodiversity of and ecosystem functions performed by minibeasts in restored habitats.

Fig. 3 The introduced Portuguese millipede, Ommatoiulus moreletii
Fig. 4 Revegetated farmland
Further reading: P Contos, JL Wood, NP Murphy, H Gibb (2021) Rewilding with invertebrates and microbes to restore ecosystems: Present trends and future directions. Ecology and Evolution 11 (12), 7187-7200.
P Contos, NP Murphy, H Gibb (2023) Whole‐of‐community invertebrate rewilding: Leaf litter transplants rapidly increase beetle diversity during restoration. Ecological Applications 33 (2), e2779.