Summary/Abstract
Climate change is expected to affect vegetation: associated rising atmospheric CO2, higher temperatures and more variable and extreme rainfall regimes can all cause major shifts in vegetation composition, structure and function. Such effects need to be detected to confirm understanding and to inform models that can predict future vegetation change and guide management efforts. However, many change drivers—some related to, and others distinct from, climate change—simultaneously affect vegetation. These drivers include altered land management practices and shifts in fire and grazing regimes. Untangling the signals of climate-change-induced vegetation change from these other drivers of variation poses significant challenges. These challenges are amplified in regions with high interdecadal climate variability and enduring legacies of shifting human activities.
Here, the authors assess attempts to detect and attribute vegetation change across Australia, a continent that exemplifies such complexities. The authors develop a scheme to classify attribution efforts according to whether they consider (1) qualitative or quantitative evidence, (2) mechanistic explanations and (3) alternative plausible change drivers. While a significant body of evidence demonstrates vegetation change in Australia, the authors find that it is difficult to confidently attribute changes to recent climate shifts—noting that few studies have attempted to do so. Several recommendations emerge that may improve attribution worldwide, including explicitly considering attribution strength, committing to long-term monitoring of vegetation and change drivers and recognising multiple drivers of change, especially past and present human influences. Finally, the authors suggest that achieving the strongest level of attribution requires linking observations and mechanistic models.