Risks to carbon dynamics in semi-arid woodlands of eastern Australia under current and future climates

Rachael H Nolan; Jennifer Sinclair; Cathleen M Waters; Patrick J Mitchell; David J Eldridge; Keryn I Paul; Stephen Roxburgh; Don W Butler; Daniel Ramp

doi:10.1016/j.jenvman.2019.01.076

Risks to carbon dynamics in semi-arid woodlands of eastern Australia under current and future climates

J Environ Manage. 2019 Apr 1:235:500-510. doi: 10.1016/j.jenvman.2019.01.076. Epub 2019 Jan 31.

Authors

Rachael H Nolan¹, Jennifer Sinclair², Cathleen M Waters³, Patrick J Mitchell⁴, David J Eldridge⁵, Keryn I Paul⁶, Stephen Roxburgh⁶, Don W Butler⁷, Daniel Ramp⁸

Affiliations

¹ School of Life Sciences, University of Technology Sydney, PO Box 123, Broadway, NSW 2007, Australia; Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW, 2751, Australia. Electronic address: Rachael.Nolan@WesternSydney.edu.au.
² School of Life Sciences, University of Technology Sydney, PO Box 123, Broadway, NSW 2007, Australia; GreenCollar, The Rocks, Sydney, NSW, 2000, Australia.
³ New South Wales Department of Primary Industries, Climate Research, Orange, New South Wales, 2800, Australia.
⁴ CSIRO Land and Water, Sandy Bay, Tasmania, 7005, Australia.
⁵ Centre for Ecosystem Science, School of Biological, Earth and Environmental Sciences, University of New South Wales, NSW, 2052, Australia.
⁶ CSIRO Land and Water Flagship, Canberra, Australian Capital Territory, 2601, Australia.
⁷ Queensland Herbarium, Toowong, Queensland, 4066, Australia.
⁸ School of Life Sciences, University of Technology Sydney, PO Box 123, Broadway, NSW 2007, Australia.

PMID: 30711835
DOI: 10.1016/j.jenvman.2019.01.076

Abstract

Extreme disturbance events, such as wildfire and drought, have large impacts on carbon storage and sequestration of forests and woodlands globally. Here, we present a modelling approach that assesses the relative impact of disturbances on carbon storage and sequestration, and how this will alter under climate change. Our case study is semi-arid Australia where large areas of land are managed to offset over 122 million tonnes of anthropogenic carbon emissions over a 100-year period. These carbon offsets include mature vegetation that has been protected from clearing and regenerating vegetation on degraded agricultural land. We use a Bayesian Network model to combine multiple probabilistic models of the risk posed by fire, drought, grazing and recruitment failure to carbon dynamics. The model is parameterised from a review of relevant literature and additional quantitative analyses presented here. We found that the risk of vegetation becoming a net source of carbon due to a mortality event, or failing to realise maximum sequestration potential, through recruitment failure in regenerating vegetation, was primarily a function of rainfall in this semi-arid environment. However, the relative size of an emissions event varied across vegetation communities depending on plant attributes, specifically resprouting capacity. Modelled climate change effects were variable, depending on the climate change projection used. Under 'best-case' or 'most-likely' climate scenarios for 2050, similar or increased projections of mean annual precipitation, associated with a build-up of fuel, were expected to drive an increase in fire activity (a 40-160% increase), but a decrease in drought (a 20-35% decrease). Under a 'worst-case' climate scenario, fire activity was expected to decline (a 37% decrease), but drought conditions remain similar (a 5% decrease). These projected changes to the frequency of drought and fire increase the risk that vegetation used for carbon offsetting will fail to provide anticipated amounts of carbon abatement over their lifetime.

Keywords: Climate change; Drought; Forest; Grazing; Mortality; Wildfire.

MeSH terms

Australia
Bayes Theorem
Carbon*
Climate Change
Forests*

Substances

Carbon