Ecosystem-based management aims to balance human activities with environmental stewardship to maintain ecosystem properties, functions and services. This requires an appreciation of how human activities interact and affect different ecosystem components (Halpern et al. 2008, Levin et al. 2009, Ban et al. 2010, Curtin & Prellezo 2010). These interactions are known as cumulative impacts, and can result from separate pressures within an activity or interacting pressures from multiple activities (Figure MAR39). Robust assessments of interactions, however, is extremely difficult, as interactions are likely to be nonlinear and may be synergistic (working together) or antagonistic (working against each other). The sectoral approach to marine management in Australia often does not account for the additive or multiplicative effects of activities, which can be a key risk to the environment.
Cumulative impacts and management of multiple uses
Cumulative impacts and management of multiple uses
Analysis and mapping of cumulative impacts in the marine environment is an expanding research area (Crain et al. 2008, Halpern et al. 2009, Ban et al. 2010, Halpern & Fujita 2013). It also assists with conservation and marine spatial planning by identifying key areas for planning to focus on (Dunstan et al. 2016). Mapping cumulative impacts, however, requires spatially explicit information on habitats, communities and species groups, human uses, the pressures generated by human uses and any feedbacks within the system—information that is frequently unavailable. In some situations, cumulative impacts can be determined from statistical analysis of existing data (e.g. Foster et al. 2015). In others, many assumptions need to be made about the cumulative nature of impacts themselves and the responses of the marine environment to these impacts (Anthony et al. 2013). Most attempts at estimating cumulative impacts have taken a linear, additive approach (e.g. layering the footprints of various industries within a geographic information system framework), rather than recognising the true combinatory nature of cumulative effects and the varying footprints of different industries.
Within the Australian marine environment, work on developing methods that assess the cumulative nature of multiple impact sources is also expanding. Some sectors have identified the need to incorporate such research into management frameworks for better accounting of cumulative impacts; for example, AFMA and the Commonwealth Fisheries Research Advisory Board have identified developing cumulative risk assessment methods as a priority for research. Work to date includes assessing:
- the impact of multiple environmental pressures (e.g. Butler et al. 2015)
- the temporal additive or multiplicative nature of single-source impacts associated with industry, such as particular types of fishing, on habitats and communities (e.g. Foster et al. 2015, Pitcher et al. 2016a; see Box MAR2)
- multiple-source impacts associated with the environment and industry (e.g. Fulton et al. 2011b, Zhou et al. 2013).
Methods used range from simple effect–response models to complex ecosystem models, with novel combinations of qualitative and probabilistic models providing new options (Anthony et al. 2013).
A review of the management effectiveness of the Great Barrier Reef Marine Park identified that the cumulative and consequential impacts on biodiversity were not well understood. As a result, no explicit strategies or action plans existed for addressing these, particularly in relation to degradation of the southern inshore region of the park (Hockings et al. 2014). In response, the Reef 2050 Long-term Sustainability Plan sets out a series of key actions for managing the cumulative nature of pressures on the Great Barrier Reef (Australian Government & Queensland Government 2015). Approval processes under the EPBC Act have the intent of broad system-level consideration of cumulative effects (see also Managing for resilience). However, little practical guidance is provided on how the cumulative nature of impacts, even if identified, can be assessed.
Truly integrated management of the marine environment should bring the principles of ecosystem-based management, sea-use management and marine spatial planning into 1 framework. This framework should allow for the multiple uses of the marine environment, while ensuring that ecosystem structure, functioning and services are maintained, and that safeguards are in place to protect components of marine ecosystems (Ehler & Douvere 2007). The reality is that ecosystem-based and integrated management mean different things to different people and different sectors.
Uptake of integrated approaches to the management of natural resources has been slow, and, although such an approach may have been adopted at a policy level, practical implementation is limited (Garcia et al. 2003, Smith et al. 2007). For example, although Australian Government, and state and territory fisheries management agencies have adopted ecosystem-based fisheries management as the approach to future management in principle (Smith et al. 2007), most management frameworks concentrate on individual fish populations strictly in demographic terms. That is, they account for the input of individuals as population growth or immigration, and the output in terms of natural and fishing mortality. Few fishery management frameworks explicitly account for variability in external factors, such as predator and prey abundances, and variability in the biophysical environment, and the impacts of changes in the abundance of populations on the surrounding ecosystems. Although the science may be available to support comparisons of alternative management options at the general strategic level (Fulton et al. 2011a, 2014), quantitative assessment and evaluation require simpler models that can be fitted to data (Plagányi et al. 2014). New approaches, however, are starting to become available and to be tested (e.g. Dichmont et al. 2016). Tight resource constraints have a major impact on the capacity of jurisdictions to implement what has been identified as best practice and aspirational. This will be a constraining factor into the foreseeable future for ecosystem-based fisheries management and the management of other marine activities.
Although monitoring programs are in place for the Great Barrier Reef Marine Park, allowing the identification and evaluation of cumulative impacts, management has largely focused on individual elements or activities within the park, and spatial planning only manages some activities (Hockings et al. 2009). In particular, differences in legislation, policy, planning, and actions addressing pressures and impacts across jurisdictions have been identified as inhibiting effective management of the region (Hockings et al. 2009). The Reef 2050 Long-term Sustainability Plan (Australian Government & Queensland Government 2015) aims to include all levels of government, the community, traditional owners, industry and the scientific community in the management of external pressures affecting the reef (e.g. water quality and dredge disposal). A Reef-wide integrated monitoring and reporting program is currently being developed to measure the success of the plan and support adaptive management of the World Heritage Area (Hedge et al. 2013).