Biodiversity Matters for Resilience of Environmental Plantings

Southwestern Australia is an obvious place for action on biodiversity loss. Habitat destruction and fragmentation of its agricultural landscapes, urban development, and resource extraction have been vast and consequential (Yates et al., 2010; Raiter et al., 2017; Pettit et al., 2015). Many regions have had native vegetation cleared below safe ecological limits, such as the Wheatbelt where only 7% remains (Prober & Smith, 2009).

More recently, climate change has exacerbated the impacts of human activity in Southwestern Australia. Future projections of rainfall reductions and increased extreme weather events will limit agricultural production on some farms (Sudmeyer et al., 2016). There is a generational opportunity to use this unproductive land for ecosystem restoration projects that build biodiversity and carbon back into these landscapes, and reverse environmental degradation. These projects should be guided by best practice to achieve their potential environmental and biodiversity benefits.

The Australian Carbon Credit Unit (ACCU) Scheme provides the opportunity to generate carbon credits by planting mixed-species or mallee under the Reforestation by Environmental or Mallee Plantings—FullCAM Methodology Determination 2024. Additionally, the Nature Repair Act 2023 provides the opportunity to generate biodiversity credits by planting vegetation under the Nature Repair (Replanting Native Forest and Woodland Ecosystems) Methodology Determination 2025. Done right, proponents can claim both carbon and biodiversity credits from the same project.

Currently, the methodology determinations include detailed instructions for proponents, including the use of local ‘reference’ native vegetation to guide species selection for projects. For example, there are requirements on seed sourcing for the carbon credit scheme (i.e., that seeds be collected from within the natural distribution of the species and appropriate for biophysical characteristics of the area planting). However, the methodologies lack guidance on the number of species to plant. The unstated assumption appears to be that species will return in time. The reality is that plant species do not disperse easily in the fragmented Wheatbelt landscape (Standish et al., 2007). Herbs, for example, do not tend to recover by themselves in biodiverse reforestation plantings (Pankhurst et al., 2021). This understorey layer is critical to biodiversity and ecological function.

Projects may fail without diversity to underpin ecological resilience to disturbances, including climate-induced disturbances such as drought (Standish & Prober, 2020). This is because diverse planted forests are more likely to contain the variety of responses needed to maintain resilience in the face of multiple disturbances such as fire and flood (Standish & Pankhurst, 2024). If one species is destroyed by a pest, then other, pest-resistant species, can fulfil its ecological function until it recovers. The methodologies require ecological resilience but lack the guidance on how to achieve it.

The lack of guidance in the legislation leaves room for proponents to establish species-poor projects that a) do not contribute meaningfully to biodiversity outcomes and b) are not resilient to extreme climate events (e.g., drought, flood). Projects may fail, and failure will lead to uncertainty among potential investors in the nature repair market. Australia cannot afford to let this happen (Mappin et al., 2022). Moving forward, it is critical that biodiverse plantings aim to restore the biodiversity of the reference ecosystem and not just a fraction of it.

Citations

Yates, C. J., McNeill, A., Elith, J. & Midgley, G.F. (2010). ’Assessing the impacts of climate change and land transformation on Banksia in the South West Australian Floristic Region.’ Diversity and Distributions, 16, pp.187–201

Raiter, K. G., Prober, S. M., Hobbs, R. J. & Possingham, H. P. (2017). ’Lines in the sand: quantifying the cumulative development footprint in the world’s largest remaining temperate woodland.’ Landscape Ecology, 32, pp. 1969–1986

Pettit, N. E., Naiman R. J., Fry, J. M. Roberts, D. J., Close, P. G. et al. (2015). ’Environmental change: prospects for conservation and agriculture in a southwest Australia biodiversity hotspot.’ Ecology and Society, 20(3), p.10.

Prober, S. M., & Smith, F. S. (2009). ’Enhancing biodiversity persistence in intensively used agricultural landscapes: A synthesis of 30years of research in the Western Australian wheatbelt.’ Agriculture, Ecosystems & Environment, 132, pp. 173–191

Sudmeyer, R., Edward, A., Fazakerley, V., Simpkin, L., & Foster, I. (2016). ’Climate change: impacts and adaptation for agriculture in Western Australia.’ Bulletin 4870, Department of Agriculture and Food, Western Australia, Perth

Standish, R. J., Cramer, V. A., Wild, S. L., & Hobbs, R. J. (2007). ’Seed dispersal and recruitment limitation are barriers to native recolonisation of old-fields in Western Australia.’ Journal of Applied Ecology, 44, p.435–445.

Parkhurst, T., Prober, S. M., & Standish, R. J. (2021). ’Recovery of woody but not herbaceous native flora 10 years post old-field restoration.’ Ecological Solutions and Evidence 2, e12097

Standish, R. J., & Prober, S. M. (2020). ’Potential benefits of biodiversity to Australian vegetation projects registered with the Emissions Reduction Fund—is there a carbon-biodiversity trade-off?’ Ecological Management and Restoration 21, p.165–172

Standish, R. J., & Parkhurst, T. (2024). ’Interventions for resilient nature-based solutions: an ecological perspective.’ Journal of Ecology 112, p.2502–2509.

Mappin, B., Ward, A., Hughes, L., et al. (2022). ’The costs and benefits of restoring a continent’s terrestrial ecosystems.’ Journal of Applied Ecology, 59, p.408–419