Recovery Dynamics in Benthic Communities: Balancing Detail with Simplification
309
rapidly growing mobile species. Larger, longer-lived and less mobile species
would become increasingly rare. Although effects may be more apparent in
the upper reaches of the estuary, they are probably more significant in the
channels and sand flats because of the inherently higher diversity of these
habitats.
14.6. Recovery: a Useful Tool for Assessing Broad-Scale and
Cumulative Effects?
Our comparisons of recovery of macrobenthic communities highlight some
of the difficulties that require resolution in order to use "recovery time"
(resilience) as an indicator of ecosystem health. There is growing concern
about chronic broad-scale degradative change in natural ecosystems and how
to collect appropriate data to monitor and assess trends. The merging of
socio-economic, policy and scientific concepts and concerns over global
environmental change has focused attention on the concept of ecosystem
health (Rapport et al. 1998). This concept has been strongly debated in the
scientific literature because of the difficulties of measurement and inference
(e.g., Calow 1992; Suter 1993). Nevertheless, assessment techniques have been
proposed and the time taken to recover from disturbance is usually considered a key factor in determining environmental health (Shraderfrechette
1994; Mageau et al. 1995). Developing consistent experimental methodologies
to assess resilience would be reasonably straightforward; the trick is comparing responses across systems that vary in environmental characteristics
(particularly hydrodynamic conditions). Site history will influence the supply
of available colonists, both by direct influences on benthic communities and
in the broad-scale spatial arrangement of the habitat matrix. Macrobenthic
communities in degraded ecosystems typically are dominated by small,
rapidly growing and highly mobile species, which result in the rapid recovery
of small-scale disturbances (e.g., Pearson and Rosenberg 1978; Rhoads et al.
1978). Most importantly, we must be aware of the important problem of
"shifting baselines" which plagues comparisons when information on site
history is unavailable (Leppakoski 1975; Dayton et al. 1998). Measuring the
resilience of macrobenthic communities may well result in a counter-intuitive
assessment of ecosystem health, because degraded benthic communities will
recover from disturbances quickly and we may not have sufficient knowledge
to define site history.
309
rapidly growing mobile species. Larger, longer-lived and less mobile species
would become increasingly rare. Although effects may be more apparent in
the upper reaches of the estuary, they are probably more significant in the
channels and sand flats because of the inherently higher diversity of these
habitats.
14.6. Recovery: a Useful Tool for Assessing Broad-Scale and
Cumulative Effects?
Our comparisons of recovery of macrobenthic communities highlight some
of the difficulties that require resolution in order to use "recovery time"
(resilience) as an indicator of ecosystem health. There is growing concern
about chronic broad-scale degradative change in natural ecosystems and how
to collect appropriate data to monitor and assess trends. The merging of
socio-economic, policy and scientific concepts and concerns over global
environmental change has focused attention on the concept of ecosystem
health (Rapport et al. 1998). This concept has been strongly debated in the
scientific literature because of the difficulties of measurement and inference
(e.g., Calow 1992; Suter 1993). Nevertheless, assessment techniques have been
proposed and the time taken to recover from disturbance is usually considered a key factor in determining environmental health (Shraderfrechette
1994; Mageau et al. 1995). Developing consistent experimental methodologies
to assess resilience would be reasonably straightforward; the trick is comparing responses across systems that vary in environmental characteristics
(particularly hydrodynamic conditions). Site history will influence the supply
of available colonists, both by direct influences on benthic communities and
in the broad-scale spatial arrangement of the habitat matrix. Macrobenthic
communities in degraded ecosystems typically are dominated by small,
rapidly growing and highly mobile species, which result in the rapid recovery
of small-scale disturbances (e.g., Pearson and Rosenberg 1978; Rhoads et al.
1978). Most importantly, we must be aware of the important problem of
"shifting baselines" which plagues comparisons when information on site
history is unavailable (Leppakoski 1975; Dayton et al. 1998). Measuring the
resilience of macrobenthic communities may well result in a counter-intuitive
assessment of ecosystem health, because degraded benthic communities will
recover from disturbances quickly and we may not have sufficient knowledge
to define site history.