Specified resilience is the resilience of a system to known or expected pressures. The adaptive capacity of species and ecosystems is the extent to which they can maintain their resilience in the face of these pressures. The process of natural selection has meant that species and ecosystems are well adapted to the pressures they have experienced in the past. They are not necessarily adapted to future pressures if these are different from those of the past. Steffen et al.1 concluded that a wide range of species is potentially vulnerable to aspects of climate change, because species could be exposed to conditions that are outside their capacity to adapt. Table 8.25 summarises conclusions from a major recent national study about the characteristics of Australian native species that are likely to make them more or less vulnerable to the impacts of climate change.
Similarly, pressures like altered fire regimes, pests and diseases, grazing, altered hydrological regimes and land clearing potentially have impacts on species and ecosystems that are outside their capacity to adapt.
|Aspects of species’ physiology and life history||Characteristics of species least at risk||Characteristics of species most at risk||Examples|
|Physiological tolerance to environmental factors such as temperature, water availability and fire||Broad tolerance||Narrow tolerance||Many diseases and pests are likely to become more invasive, while many native species may become more susceptible (e.g. amphibians are likely to become more susceptible to attack by the chytrid fungus); some reptiles (e.g. crocodiles and turtles) change the ratio of male to female offspring as temperature rises; plants and slow-moving animals are likely to be especially vulnerable to changed fire regimes|
|Phenotypic plasticity (the ability of individuals to vary aspects of their physiology and/or life history in response to environmental changes, without changes to their genetic makeup)||High plasticity||Low plasticity||Weeds and pests are often species with high phenotypic plasticity (be they introduced or native species). Native species can become widespread and abundant when environmental conditions change (e.g. some kangaroos when watering points are available, some parrots in cities and towns, bush flies in agricultural areas)|
|Genetic variability (the variation in genes between individuals of a species, which affects the range of physiological and life history attributes that may be present in future generations)||High variability||Low variability||The ability of species to thrive over wide ranges or adapt to changed environments (such as those in the row above) are due partly to genetic variation that allows for natural selection of individuals that do well in a new environment. Species that have gone through major declines in numbers (e.g. many rare and threatened species) have often suffered reductions in genetic variability|
|Generation times (time from conception to independence) and time to sexual maturity||Short generation time||Long generation time||Invertebrates (e.g. insects, spiders and others) are likely to be more responsive due to short generation times and the ability to disperse rapidly; long-lived trees are likely to be more vulnerable than short-lived plants; faster growing corals may cope with rising sea levels better than slower-growing species|
|Fecundity (ability to reproduce)||High fecundity||Low fecundity||Species that produce many eggs may be at an advantage, but their survival might be affected and species that focus more on nurturing few young (e.g. mammals) might be advantaged in some situations; plants that rely on insect pollinators are susceptible if those pollinators are not present at the required time; species that require seasonal food supplies, such as fruit, to support breeding could suffer declines in fecundity; diseases and parasites can affect fecundity of many species|
|Requirements for food, nesting sites, etc.||General (broad) food requirements||Specific (narrow) food requirements||Vulnerable species include species specialised to eat certain foods (e.g. kangaroos adapted to eat low-quality grasses or birds specialising on certain seeds and fruits); a range of birds, fish, mammals, amphibians, invertebrates and other species whose food and nesting requirements are linked with flow regimes on waterways; and species (e.g. some birds and turtles) that nest on sandy shorelines|
|Dispersal capacity (ability to move through landscapes to find food, mates, nests, suitable climate, etc.)||Good capacity||Poor capacity||Species adapted to rare habitats (e.g. plants and fungi with specific soil requirements) are likely to have to travel further than others; some species will be more susceptible to predation by other species during dispersal|
|Geographic ranges||Broad ranges||Narrow ranges||Vulnerable species include species adapted to a narrow range of environments (e.g. plants and animals living in high-altitude environments, and plants adapted to specific soil types)|
Source: Adapted from Steffen et al.1
In theory, assessing specified resilience requires an understanding of known pressures and what is required for a system to cope with them. Methods to assess the specified resilience of biodiversity and biodiversity management include assessing:
- the ecological processes that allow species and ecosystems to maintain and adapt their structures and functions in the face of change (e.g. ability to move in landscapes to find food, mates and suitable climates, ability to adapt aspects of form and function to survive in changing environments, and levels and types of genetic variation that is maintained in populations as they undergo change)
- the processes in place to identify likely pressures and possible future changes in them
- how well the dynamic relationships between the forces that cause pressures (indirect drivers of change), the pressures themselves (direct drivers) and the responses of genes, species and ecosystems are understood
- the success of strategies to manage the adaptability of biodiversity and/or pressures on it.
We have not attempted to assess these aspects in detail in this report, but their consideration in future data collection at a national scale for SoE and other reporting would be a valuable resource to support managing for resilience.
The fact that most SoE reports from the states and territories over the past several reporting periods have consistently reported that the same set of pressures persist, and that efforts to reduce some of the pressures seem to be having little effect, suggests that the resilience of at least some major parts of biodiversity to these pressures is being exceeded. However, it must also be acknowledged that measures are in place for some pressures (e.g. land clearing) that would be expected to take some time to deliver positive change.