Contrasting effects of aridity and grazing intensity on multiple ecosystem functions and services in Australian woodlands

Global change is expected to reduce the provision of multiple ecosystem services in drylands, the largest biome on Earth. Understanding the relative importance of climate change and overgrazing on ecosystems services is critical for predicting the effects of global change on ecosystem well-being. We generated a system-level understanding of the effects of climate (aridity intensity) and land use intensification (herbivore grazing intensity) on four regulating ecosystem services (C-storage, N-availability and P-availability, and organic matter decomposition) and one provisioning service (plant production) in wooded drylands from eastern Australia. Climate change and grazing intensity had different effects on multiple ecosystem services. Increasing aridity from 0·19 (dry subhumid) to 0·63 (arid) had consistent suppressive effects on C-storage, N-availability, decomposition and plant biomass services, but not on P-availability. The magnitude of these suppressive effects was greater than any effects due to grazing. All sites showed evidence of kangaroo grazing, but the heaviest grazing was due to cattle (dung: range 0–4545 kg ha−1; mean 142 kg ha−1). Any effects of grazing on ecosystem services were herbivore specific and ranged from positive to neutral or negative. Sheep, and to a lesser extent cattle, were associated with greater N-availability. Rabbits, however, had a greater effect on P-availability than aridity. Our study suggests that increases in livestock grazing may fail to sustain ecosystem services because of the generally stronger negative effect of increasing aridity on most ecosystem services in our model dryland. These services are likely therefore to decline with global increases in aridity. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.