Evolution of the ecosystem approach
It is unclear how the traditional extrapolative (bottom-up) or reductionist (top-down) approaches to environmental risk assessment and management address the aspirational goals for protecting ‘biodiversity’, ‘ecosystems’ or ‘the environment as a whole’, set by legislation for the registration and authorisation of chemicals (Chapter 3). Although there is a recognition that more holistic, ecosystem-level approaches are needed (SCHER/SCENIHR/SCCS, 2012), these are beset by the inherent variation and complexity of ecosystems (Table 1.1), presenting a conundrum for environmental risk assessors and managers.
Table 1.1: Major sources of uncertainty in environmental risk assessment
| Natural background variability in the environment |
| • Spatial variation, including geology, topography / bathymetry, habitat and climate. |
| • Temporal variation, including environmental stochasticity, diurnal and seasonal cycles, longer-term environmental change e.g. climate change. |
| Representation of chemical exposure profiles |
| • Numerous possible environmental exposure scenarios, influencing both the exposure (environmental fate, bioavailability) and effects of chemicals. |
| • Spatial and temporal variability associated with chemical exposures. (Constant exposure is normally assumed in ERA). |
| Extrapolation of chemical effects |
| • Laboratory to field extrapolation i.e. from ecotoxicological tests conducted under controlled conditions (generally in the laboratory) to populations in the wild. |
| • Endpoint extrapolation from organism-level effects to population-level effects and above. |
| • Species extrapolation from a few sensitive ‘model’ species to all species in the environment, beset by inter-species and intra‑species (i.e. inter-population and site-specific) variation in vulnerability to chemicals. |
| Ecological factors, including interactions |
| • Variation in species’ ecological life-histories, which influence chemical exposure, effects and recovery. |
| • Interactions among different stress factors (physical, biological and other chemical factors) that may affect ecosystem health and interact with chemical effects. |
| • Interactions among individuals, populations and biological communities potentially leading to indirect ecological exposures (e.g. bioaccumulation and biomagnification) and chemical effects within food chains and ecosystems. |
Adapted from Chapman, 2002; Hommen et al, 2010; SCHER/SCENIHR/SCCS, 2012
The mandate for an ‘ecosystem approach’ for sustaining the Earth's biological resources, alongside economic and social development, came in 1992 with the United Nations (UN) Convention on Biological Diversity (UN, 1992a), but the concept dates back to the 1950s (Waylen et al, 2014). Crucially, the ecosystem approach recognises the importance of sustainable, self-organising and complex ecosystems, which “maintain a degree of stable functioning across time”, and that “a system is healthy if it maintains its complexity and capacity for self-organisation” (Norton, 1992). Furthermore, since ecosystems are complex systems with multiple feedback loops, trade-offs and interactions, it is not feasible to manage or protect individual species in isolation (Slocombe, 1993). Over the last two to three decades, the terms ‘ecosystem management’, ‘ecosystem approach’ and latterly the ‘ecosystem services approach’ have been used increasingly and often inter-changeably, despite subtle differences (Waylen et al, 2014).