Multiple factors acting at various levels of organisation, from species to landscapes, will interact to determine resilience capacity. For example, a species’ sensitivity to environmental change, its rate of population increase, its genetic variability and its phenotypic plasticity (i.e. the ability of a species to adjust its characteristics in response to its environment) are properties that underpin resilience (these are described in more detail in SoE 2011). At the landscape level, the amount of intact habitat, connectivity, and variation (or heterogeneity) in the landscape are important properties affecting resilience (Oliver et al. 2015; see Box BIO22).
Adaptive capacity, which is often used to refer to the set of preconditions that enable species and systems to respond to climate change, is a synonym for many characteristics of resilience. To be resilient, species, communities and systems must generally be able to buffer disturbance, reorganise and renew after disturbance, and learn and adapt. For some parts of Australia’s biodiversity, it is changes in habitat condition that most affect their resilience, whereas in other parts of their range it is changes in habitat extent. For example, in Australia during the past 5 years, we have continued to observe continental-scale decreases in migratory shorebirds. Shorebirds migrate to Australia from Siberia and northern Alaska by a migration corridor known as the East Asian–Australasian Flyway (EAAF), which is used by more than 5 million shorebirds of almost 40 species. In 2016, an analysis of decadal timeseries of surveys of these species around Australia (Clemens et al. 2016) showed that numerous species are decreasing, some at alarming rates. The analyses examined population trends at inland and coastal sites around Australia for 19 species from 1973 to 2014. Continental-scale population decreases were identified in 12 of the 19 species, and regional-scale decreases (southern Australia) in 17 of the 19 species since 2000. Although some habitat modification has happened in Australia, vast areas of feeding grounds in Asia continue to be reclaimed, significantly reducing the ability of these birds to successfully complete their migrations (Iwamura et al. 2013; Murray et al. 2014, 2015). Tasmania is the southernmost destination in the EAAF, with observed long-term decreases exceeding those observed on the Australian mainland (see Box BIO13).
New research into climate adaptation services has identified the ecological mechanisms and traits that support the intrinsic resilience of ecosystems, and facilitate their capacity to adapt and transform in response to change (Lavorel et al. 2015). Using 4 contrasted Australian ecosystems, this research suggests that 4 main mechanisms—vegetation structural diversity, the role of keystone species or functional groups, response diversity, and landscape connectivity—underpin the maintenance of ecosystem services and the reassembly of ecological communities under increasing climate change and variability. For the grassy eucalypt woodlands of south-eastern Australia, the highest priority for anticipated future pressure is maintaining perennial vegetation to reduce the risk of future desertification. For the Littoral Rainforest and Coastal Vine Thickets of eastern Australia, the maintenance of intact, diverse, connected forest stands of good quality is considered the key management requirement to support ecosystem adaptation. For the Australian Alps and South Eastern Highlands of south-eastern Australia, a greater management focus on fire-sensitive ash-type eucalypt forests, including fire suppression, fuel reduction and reseeding, is recommended. However, novel approaches to management may need to be considered in the future, such as translocating seed from resprouting montane species rather than fire-sensitive ash species. The Murray–Darling Basin contains floodplain woodlands and forests, consisting of few flood-tolerant and drought-tolerant eucalyptus and acacia species, as well as riparian woodland corridors, and chenopod shrubland and grassland in more arid regions. The study suggests that floodplain ecosystems are likely to persist under climate change, although with reduced extent and altered vegetation structure, and limits on water diversions and the restoration of water into the river systems will provide the greatest ecosystem resilience.
- elevationally restricted mountain ecosystems
- tropical savannas
- coastal floodplains and wetlands
- coral reefs
- drier rainforests
- wetlands and floodplains in the Murray–Darling Basin
- the Mediterranean ecosystems of south-western Australia
- offshore islands
- temperate eucalypt forests
- saltmarshes and mangroves.
Key factors predisposing these ecosystems to tipping points include:
- having a restricted distribution or a narrow environmental envelope
- having suffered substantial fragmentation
- relying on critical ‘framework’ species (such as 1 or a few species of canopy trees, or coral-building organisms)
- being constrained by close proximity to humans or human activities
- already existing close to an environmental threshold.
The researchers emphasised that most vulnerable ecosystems were influenced by multiple drivers, such as climate change and extreme events, changes in fire regimes, invasive species and land-use pressures.