Are we really heading for ‘insectageddon’? Characterising changes in Eucalypt invertebrate communities under rising CO2

By 08/04/2019Current Projects
HSF 19084 | Amount: $84,000 | Project Leader: S Johnson | Project Period: Jul ’19 – Jul ‘22

A project undertaken at Hawkesbury Institute for the Environment, Western Sydney University, and supervised by Scott Johnson.

Invertebrates are the most numerous and abundant animals on the planet. They underpin the majority of plant-based food webs and drive an array of ecosystem processes, including many ecosystem services such as pollination, nutrient cycling and pest suppression. There is increasing concern that invertebrate populations are in decline because of anthropogenic factors, including a rapidly changing climate. Despite high profile claims that invertebrate populations will collapse, labelled ‘Insectageddon’ in the media, we have very little empirical information about how invertebrate communities, as a whole, will respond to climate change. We are now conducting a three-year study of invertebrate communities within a native Eucalypt woodland subjected to current and future (+150ppm) concentrations of CO2.

Fig. 1. EucFACE rings fumigate areas of native woodland with ambient and elevated concentrations of atmospheric CO2.

The EucFACE (Eucalyptus Free Air CO2 Enrichment) platform has been maintaining these CO2 in separate sections of the woodland since 2012 (Fig. 1). Of concern, an early (2013–15) analysis of invertebrates at the site suggested that populations had already declined by around 14% under elevated CO2 conditions (Facey et al., 2017). It remains unclear, however, which species were in decline, whether significant groups (e.g. pollinators) were affected or if populations have now stabilised. In 2019 we started a new project to collect invertebrate samples in the understorey and canopy of the woodland (Fig. 2).

Fig. 2. Previous sampling of invertebrates involved taxonomic identification. In this project we will use DNA metabarcoding techniques.

This project will use powerful DNA metabarcoding to ascribe invertebrates to either species or family. This technique looks at the DNA from collections of invertebrates and uses this information to tell us how many species and in what proportions they are present in particular communities.  We will use this information to determine whether elevated CO2 is altering invertebrate community diversity, composition and whether certain groups are more affected than others. This will be important for filling a significant knowledge gap in our understanding of how invertebrate communities respond to climate and atmospheric change. To our knowledge, this will be the first study to provide a highly detailed characterisation invertebrate community under elevated CO2 conditions in any Australian ecosystem.

Facey, S.L., Fidler, D.B., Rowe, R.C., Bromfield, L.M., Nooten, S.S., Staley, J.T., . . . Johnson, S.N. (2017) Atmospheric change causes declines in woodland arthropods and impacts specific trophic groups. Agricultural and Forest Entomology, 19, 101-112.