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Lake sediments are natural archives that record the response of a lake to both in-lake processes and catchment disturbance (over a range of timescales). The response (or lack of) of a lake to external forcing is a function of the severity of the disturbance (and its areal extent) but is also strongly mediated by catchment characteristics, such as slope and hydrological connectivity. Many studies of recent lake disturbance have focussed on anthropogenic disruption of geochemical cycles, e.g. acidification and eutrophication, which because of their “ecological” power appear to over-ride catchment filters. Lake sediments also record the variability of natural disturbance regimes themselves (fire, volcanic ash falls, species invasions, and climate) and the consequent lake response but this aspect has received much less attention. The possibility of using lake sediments to address long-term (102 – 103 yr) interactions between e.g., climate, catchment ontogeny and disturbance events (and their synergies) has not been fully explored, largely because of an over-riding emphasis on climate as a direct driver of ecological change.
Traditionally, limnology has also focussed on a few key sites (sentinels) but in response to the development of landscape ecology has progressively embraced a regional approach to understanding how lakes respond to external forcing (climate) and disturbance (“lakes in the landscape”). Although the interaction of a lake with its catchment is implicit, i.e. via hydrological and nutrient loading, palaeolimnologists rarely take an explicitly spatial view of this interaction nor have they considered spatial location (i.e. response of a number of lakes within a lake district). Arguably, the inherent spatial variability of terrestrial disturbance has been ignored by palaeolimnologists, largely as a result of focussing on one core from a single lake.
This paper reviews the impact of terrestrial disturbance on lakes but also argues for explicit consideration of space and location in determining the resultant temporal variability of the ecological response. The importance of within-lake spatial heterogeneity is also high-lighted (i.e. the major contribution of the littoral zone to both diversity and production). However, any attempt to determine spatially replicated (i.e. at a regional scale), holistic (i.e. whole lake) responses to disturbance will encounter considerable problems associated with dating, loss of temporal resolution and among site comparison. Despite this, it is clear that recent methodological developments in the area of biomarkers, compound specific stable isotopes coupled with progress in dating (age-models), ecological modelling and statistical analysis offer the possibility of undertaking regionally-replicated studies of lake response to natural disturbance, thereby contributing and expanding our understanding of ecosystem dynamics at a range of spatial and temporal scales.
‘The history of streams and rivers is as much a social and technological history as it is a scientific one.’ (Petts, 2001)
‘Too often, imperfect analyses combine with conflicting socio-economic interests and politics to limit rehabilitation success.’ (Booth et al., 2004)
‘Restoring the river costs money, lots of it. Critics argue that we can't afford to restore a river for a few endangered fish or birds.’ Public statement about the Missouri restoration work, quoted by Marain Maas in a lecture to the Water Protection Network, 18–20 March 2012.
In industrialised countries over the last sixty years a combination of new laws, technological advances, scientific developments, commercial and economical changes, and public and political opinion has resulted in the chemical and ecological recovery of many rivers that have been polluted over centuries. Improvements to water quality have been directly and positively linked — through both experimentation and the long-term monitoring of chemical and ecological conditions — to ecological enhancement, usually measured in terms of taxon richness or community diversity and expressed as readily interpretable indices.
Ecological enhancement has often been used as the major reasoning behind efforts to restore rivers to their natural hydro-geomorphic (geographical, geological and hydrological) condition, based on the hypothesis that increasing hydro-geomorphic diversity in river catchments and floodplains will in turn increase the natural diversity of living organisms. However, direct studies and metadata analyses demonstrate that any relationship between physical restoration and ecological indicators is at best uncertain and at worst neither quantified nor readily quantifiable, and even the physical results of such restoration projects have not always met expectations, with many schemes failing for various reasons.
In this article we propose that it is not the potential improvements to the ecology or the physical characteristics of the rivers (hydromorphology) that has been of primary importance when deciding to carry out restoration projects; instead it is a drive by the global finance industry to deliver flood alleviation schemes and thus save huge compensation payments, and political expediency where public opinion has reacted strongly against flooding. Evidence includes the continued planning of such projects under the guise of ecological improvements, even in the light of the clear physical and ecological failures of many completed river restorations. Since the success or failure of such proposals is measured often by public attitudes and subjective opinions, ecological consequences are often not measured. However, advances in science and the involvement of ecologists with distinguished careers and high integrity may have provided scientific gravitas to facilitate acceptance of the plans.
We also explore some of the unintended commercial and social consequences of pollution controls in the UK during the 1960s, including accelerated industrial emigration, which in turn had significant and predictable repercussions in developing countries such as China and India. The effects these consequences will have on future restorations and pollution controls are considered, as well as potential international social, political, commercial and economic requirements particularly in newer and future industrialised countries.