Lake ecosystems and the valuable services they provide, including drinking water, game fish biomass or recreation, are jeopardized by the negative environmental impacts of human activities. Jani Heino and David G. Angeler list three issues that should be taken into account in the monitoring and sustainable management of lake ecosystems in the Anthropocene.
The Anthropocene, our current era, presents formidable threats to the services provided by all ecosystems, and lakes are no exception. The increasing anthropogenic, meaning human-caused, impacts on lakes jeopardize essential ecosystem services, such as drinking water, water for irrigation, fish, hydropower, recreation, tourism and aesthetic values, through detrimental effects on biodiversity and geodiversity . Biodiversity − the numbers and kinds of living organisms − and geodiversity − abiotic earth materials, forms and processes − are essential building blocks underlying ecosystem services.
If bio- and geodiversity are negatively impacted by anthropogenic environmental changes, such as climate change, land-use change, eutrophication and pollution, we should find better means to monitor and subsequently counter these negative impacts. There are at least three key issues that should be taken into account when thinking of the monitoring and sustainable management of lake ecosystems and the services they provide.
1. Focus on entire catchments
We should focus on entire catchments and understand the degree to which anthropogenic impacts modify them and their critical features. This is because catchment land cover and land use largely determine the abiotic conditions for lakes embedded in a given catchment. For example, lakes bordered by forests versus agricultural fields often exhibit different nutrient concentrations, affecting water quality and subsequent use of raw water supplies. In addition, lakes in urban catchments as opposed to those in more natural areas often receive considerable amounts of contaminants and pollutants.
2. Take note on the lake’s position in the landscape
We should emphasise the importance of a lake’s position in the landscape and its connections with other freshwater ecosystems. This is important because no lake is perfectly isolated from its surrounding landscape and other lakes. For example, lakes situated low in the landscape are more likely to receive large amounts of material, contaminants and pollutants from the lakes situated higher in the landscape. In addition, a lake’s position in the landscape largely determines its biodiversity.
Lakes situated low in the landscape are likely to be large in surface area, which increases biodiversity (e.g. number of fish species), and are more likely to receive more organisms dispersing between lakes across the landscape. This increases the probability that local extinctions of species are countered by recurring colonization.
If natural environmental conditions of lakes or connectivity between lakes are negatively impacted, there will be consequent negative impacts on biodiversity. When biodiversity decreases, many ecosystem services may also be negatively affected. This can potentially include production of game fish biomass, water purification processes, recreation and aesthetic values. The factors affecting biodiversity and ecosystem services should thus be considered in a context that perceives lakes as parts of larger “waterscapes”, where organisms and material, of both natural and anthropogenic origin, are constantly moving within and among lakes.
3. Consider the context of larger waterscapes
Besides, monitoring, lakes and their ecosystem services should also be managed in the context of larger waterscapes. Here, it is essential to understand the spatial and temporal variation in abiotic conditions and biodiversity. However, such dynamism presents challenges to monitoring and managing lakes. This is because modelling or forecasting so-called ‘non-stationary processes’ is very difficult.
An example of a non-stationary phenomena is that ecosystems have a tendency to undergo catastrophic shifts. In lakes, such regime shifts can happen, for example, because of eutrophication. Eutrophication and associated regime shifts threaten the services lakes provide to humans, such as fishing, recreation and aesthetic values, and are also often connected with harmful algal blooms. Lakes cannot recover from anthropogenic disturbances indefinitely. Once the capacity of lakes to recover from anthropogenic disturbances has been lost, impacted and heavily degraded lakes may not be able to return to the desired clear-water regime without costly and extensive management efforts.
The three key issues highlighted above emphasize the paucity of information of systemic features that contribute to biodiversity and ecosystem services of lakes. Currently, inadequate monitoring data often results in uncertain predictions. To reduce such uncertainty, environmental managers should implement a framework incorporating adaptive management, inference and modelling of lake ecosystems.
For example, based on existing scientific information, specific hypotheses about risks resulting from different impacts (e.g. nutrient inputs) could be coined. Environmental managers could subsequently consider management actions as hypothetical cases and assess the outcomes. This contributes to decreasing uncertainty in lake management and offers knowledge of the role of preventive or restorative measures, as well as what kind of interventions would show most promise.
The management of lakes should be grounded on knowledge on how locally-acting processes and regional-level phenomena as well as anthropogenic stressors associated with them vary in determining levels of biodiversity and quantities of ecosystem services. This knowledge should be integrated in the adaptive management of lake ecosystems in the Anthropocene. For example, BlueAdapt paves the way for promising new avenues for monitoring and securing the sustainability and resilience of lake ecosystems. This requires better use of ecological data by developing novel socio-ecological models to increase predictive understanding of lake biodiversity and ecosystem services.
The author Jani Heino is a Senior Research Scientist at the Freshwater Centre of the Finnish Environment Institute. The author David G. Angeler is an Associate Professor at the Swedish University of Agricultural Sciences, Uppsala, Sweden.
Suggested further reading:
Angeler, D.G. et al. (2015). Linking degradation status with ecosystem vulnerability to environmental change. Oecologia, 178, 899–913.
Olden, J. et al. (2001). Spatial isolation and fish communities in drainage lakes. Oecologia, 127, 572-585.
Soininen, J. et al. (2015). Toward more integrated ecosystem research in aquatic and terrestrial environments. BioScience, 65, 174-182.
Sorrano, P. et al. (1999). Spatial variation among lakes within landscapes: Ecological organization along lake chains. Ecosystems, 2, 395-410.