The ability of ecosystems to tolerate and recover from disturbance is a phenomenon that is vitally important to understand. Resilience has stimulated much valuable research that has provided new insights into the ecological processes influencing ecosystem persistence and recovery. However, use of the concept of resilience in policy and strategies is often quite ambiguous, and evidence-based approaches to its measurement are very difficult to apply (Standish et al. 2014, Newton 2016). Effectiveness of biodiversity management shows that we struggle to measure the effectiveness of our investments in biodiversity management and the reduction of pressures. Evaluating the effectiveness of any policy or management program designed to strengthen resilience will require greater clarity around how resilience is translated into action, and clearly articulated measurement and monitoring targets.
In a management context, there are several pressing questions concerning resilience. How much disturbance can an ecosystem absorb before switching to another state? Where is the threshold associated with the switch between ecosystem states? Will ecosystems recover from disturbance without intervention (Standish et al. 2014)?
Making the concept of resilience operational to management requires finding ways to quantitatively measure it. The concept of tipping points and thresholds is often linked with the measurement of resilience. The tipping point is an ecological threshold beyond which major change becomes inevitable and is often very difficult to reverse. Direct experimental data on thresholds are usually too difficult to obtain, but observational data from ecosystems in different stages post-disturbance can be used to direct management decisions and priorities. In particular, these types of observational studies may help predict the response of ecosystems to future disturbance events of a similar nature (Standish et al. 2014).
There is some evidence that climate-driven regime shifts have already occurred in Australia. For example, researchers in southern Western Australia recently documented a relatively rapid climate-driven change in the structure and composition of Australian temperate reef communities, which, during the past 5 years, have lost their defining kelp forests and become dominated by persistent seaweed turfs (Wernberg et al. 2016). An extreme marine heatwave in 2011 and warmer than average sea temperatures in 2012 and 2013 caused a 100 kilometre contraction of kelp forests, which were replaced by seaweeds, invertebrates, corals and fishes characteristic of subtropical and tropical waters. The probability of prolonged cool conditions that could reset community structure and ecological processes to facilitate the recovery of kelp forests in this region is becoming increasingly unlikely, whereas the risk of more heatwaves that will exacerbate and expand the new tropicalised ecosystem state is increasing.
Another possible indicator of climate-driven ecosystem contraction was found in south-western Australia during the record dry and hot period of 2010 and 2011. During this drought, banksia woodlands contracted by 70–80 per cent around Perth, and more than 16,000 hectares of jarrah forest suddenly collapsed, with mortality rates more than 10 times greater than normal. This, of course, has flow-on effects to the animals that depend on them. For instance, during the same period, the population of the endangered Carnaby’s black cockatoo (Calyptorhynchus latirostris) declined by about one-third in and around Perth (Saunders et al. 2011).
At the landscape level, land managers and policy-makers are engaged in a suite of actions to build and support resilient ecosystems. These include increasing the conservation estate, reducing the impact of pressures, identifying and protecting refugia, and restoring connectivity in degraded landscapes. Land managers engaged in on-ground activities are also increasingly looking towards new approaches to improving resilience. For example, land managers involved in revegetation and restoration are beginning to incorporate ‘climate-adjusted’ or ‘composite provenancing’ strategies for a selection of species used in plantings (see Box BIO21). These strategies involve a targeted approach to enhancing the climate resilience of restoration plantings, with seed sourcing biased towards the direction of predicted climatic change (Prober et al. 2015).
A major mechanism for managing the overall resilience of biodiversity in altered landscapes is through private land conservation. Australian Government investment through NRM bodies to work with private landholders is a key factor in improving landscape function. For instance, the Victorian NRM North East Catchment Management Authority worked with private landholders to undertake a project aimed at managing approximately 600 hectares of endangered grassy woodland vegetation for biodiversity outcomes. This investment in managing threatened native vegetation on private property complements conservation through protection of remnant patches in reserves. It has been shown to support relatively species-rich assemblages of birds, including many species of conservation concern, but may have only limited benefit for protecting populations of arboreal marsupials because of the lack of hollow-bearing trees in agricultural landscapes (Michael et al. 2016).