WRITE EXTENSIVELY ON WATER CYCLE AS AN ENVIRONMENTAL SERVICE

 

INTRODUCTION

The water cycle is a biophysical process, heavily influenced by ecosystem functioning. The healthy functioning of ecosystems underpins a multitude of benefits (services) derived from ecosystems. Water is a critical component in maintaining these functions, while keeping them resilient to change (Costanza et al., 1997). The presence and absence of water in the landscape very often determines the characteristics of several supporting and regulating functions, e.g. preserving nutrients and removing pollutants (Falkenmark, 2003).

Earth is a truly unique in its abundance of water. Water is necessary to sustaining life on Earth, and helps tie together the Earth's lands, oceans, and atmosphere into an integrated system. Precipitation, evaporation, freezing and melting and condensation are all part of the hydrological cycle - a never-ending global process of water circulation from clouds to land, to the ocean, and back to the clouds. This cycling of water is intimately linked with energy exchanges among the atmosphere, ocean, and land that determine the Earth's climate and cause much of natural climate variability. The impacts of climate change and variability on the quality of human life occur primarily through changes in the water cycle. As stated in the National Research Council's report on Research Pathways for the Next Decade (NRC, 1999): "Water is at the heart of both the causes and effects of climate change."

 

 

WATER CYCLE AS AN ENVIRONMENTAL SERVICE

The concept of ecosystem services is used to analyze trade-off scenarios when human well-being and ecological sustainability need to be addressed simultaneously. The ecosystem perspective aims to bridge interdisciplinary gaps between fields as far apart as religion and biology, political science and geology or engineering and biodiversity, thereby addressing the system comprehensively.

The availability of water at any time or place, in terms of both its quantity and quality, is also a service provided by ecosystems, and one of obvious importance to agriculture. Because water is required for ecosystems to function, all ecosystem services (excepting some of those provided by marine environments, particularly oceans) are underpinned by fresh water (Aylward et al., 2005; UCC-Water, 2008).

 

Ecosystem services can be grouped into four different types (Millennium Ecosystem Assessment, 2005a), as follows:

• Provisioning services are essentially the tangible products (or goods) that are used directly by humans. These are among the most recognizable in terms of human use and are thus most frequently monetized but are not necessarily the most valuable. Relevant examples include freshwater (directly used, e.g. for drinking), energy from hydropower and all food (including all the products of agriculture, livestock rearing, forestry, fisheries and wild-caught products such as bushmeat). Globally, provisioning services have been maximized, particularly by agriculture, at the expense of reductions in other services (listed below), resulting in a serious imbalance (Millennium Ecosystem Assessment, 2005a).

• Regulatory (or ‘regulating’) services are the benefits that ecosystems provide in terms of regulating ecosystem-dependent processes. Relevant examples include: climate regulation (including precipitation), water regulation (i.e. hydrological flow), water purification and waste treatment, erosion regulation and water-related natural hazard regulation. Such services are sometimes less tangible at farm and field scales, and can be more difficult to assess economically (although there are exceptions; natural hazard regulation, for example, is more easily assessed because the impacts of disasters can often be quantified in fairly standard economic terms). In some instances, these services can be replaced by technology but often at a higher cost than that of maintaining the original service (Cairns, 1995): e.g. any infrastructure or operational costs in treating water to make it potable are essentially expenditures on replacing the original water purification and supply functions of ecosystems, which previously provided this service free.

• Cultural services include the spiritual and inspirational, religious, recreational, aesthetic and educational benefits that people derive directly or indirectly from ecosystems: for example, the recreational benefit of a lake for fi shing. Some are more easy to value (e.g. through amounts spent on recreation, including transport and accommodation costs), but others are less tangible and often difficult to quantify or monetize. Nevertheless, the importance of cultural service values should not be underestimated; they represent some of the clearest examples of the pitfalls of monetized economic valuations. An example is the case of pastoral livestock, where cultural values can override economic values in terms of development and land management, and include ‘antiquity, role in the agricultural systems, farming techniques, role in landscape, gastronomy, folklore and handicrafts’ (Gandini and Villa, 2003).

• Supporting services are those that underpin broader ecosystem functioning and

hence contribute to sustaining other services. Examples include soil formation and nutrient cycling, both of which are essentially water based and aquatic ecosystem driven processes.

 

CONCLUSIONS

The concept of ‘sustainable food production’ involves achieving the necessary increases in agricultural productivity, while simultaneously bringing the impacts of agriculture on ecosystems within manageable limits and in the face of significant resource challenges (as outlined in Chapters 1 and 2). The ecosystem setting of water within agroecosystems, and the way in which this determines the benefits (ecosystem services) that water provides, both within and beyond agriculture, offers a framework for identifying solutions to achieve sustainable agriculture. Further expansion of this approach is provided in subsequent chapters. To many readers, these concepts will not be new, but there is ample evidence that they are not being mainstreamed into agricultural planning and management.

 

REFERENCES

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Millennium Ecosystem Assessment and Island Press, Washington, DC, pp. 213–256.

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Cairns, J. Jr (1995) Editorial: Ecosystem services: an essential component of sustainable use. Environmental Health Perspectives 103 (6), 534.

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Costanza, R. et al. (1997) The value of the world’s ecosystem services and natural capital. Nature 387, 253–260. doi:10.1038/387253a0

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