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Freshwater Management Series No. 5

Guidelines for the Integrated Management of the Watershed
- Phytotechnology and Ecohydrology -

I. Socio-economic perspectives for the global application of phytotechnologies

Since the early 1990s, economists have begun to recognise the role of environment in providing "amenity" services and general life support (Victor 1991). In many cases, over-exploitation of the Earth’s ecosystems has reached the point where some of these ecosystems can no longer provide demanded benefits. Economists are now starting to consider ecosystem services as a positive, quantifiable value that must be considered in the management of environmental and economic interactions (Daily et al. 2000). An example of the application of this concept is Earth Sanctuary Ltd., a firm listed on the Australian Stock Exchange. The firm purchased 90,000 hectares of land, restored the native vegetation and wildlife, and is earning income from tourism, consulting, and wildlife-related products. The firm is also providing ecosystem services such as carbon sequestration, as well as new "environmental products" related to clean water. In addition, the firm emphasises biodiversity in its vision for forest development; timber is considered to be a "by product". An hypothetical Australian farm business in the next 20 years, in terms of ecosystem goods and services, is anticipated to derive only 65% of its income from the traditional commodities of wheat, wool, and timber. The remainder of its income would be derived from water filtration (15%), carbon sequestration (7.5%), salinity control (7.5%), and biodiversity maintenance (5%).

The key to a sustainable solution is the development and application of principles of valuation based on an integration of ecological and economic understanding. These should include:

  • Identification of ecological alternatives (e.g., constructed wetlands versus conventional mechanical sewage treatment plants).
  • Identification and measurement of impacts of alternatives based upon their full economic costs (e.g., labour, capital, and long term biophysical and social impacts).
  • Valuation and comparison of consequences of the status quo versus alternatives based on comparable units of human well-being now and in the future.

The role of human activity as a major factor in shaping the biosphere has been steadily increasing. Valuation and validation of ecosystem services provide an appropriate economic framework within which the use of phytotechnologies and ecohydrology form appropriate alternatives for the restoration of ecosystem structure and services, and management of sustainable ecosystems.

J. The "green feedback" concept

During the Earth’s evolution, interplanetary torque and solar modulation determined the sequential changes in global climatic conditions. This, in turn, determined temperatures, patterns of water supply, and distributions of plant cover. Plant cover development, as has been noted, is a function of sufficient water and energy. Plant cover helps to stabilise heat budgets by reducing temperature extremes and wind speeds. This, in turn, creates favourable conditions for further plant development and higher rates of conversion of energy, nutrients, and water into biomass. This process can be described as positive "green feedback" (Zalewski 2000).

Increased plant biomass within the landscape, especially in the temperate, subtropical, and tropical areas where energy flows have been intensive, creates good conditions for speciation and, in consequence, increased biological diversity. Under these conditions, the surplus energy accumulated in plant tissues enhances the potential for development of alternative paths of energy flow within the ecosystem. The productive and diversified structure of such plant communities, under non-catastrophic conditions and within a stabilised temperature regime, creates conditions for the diversification of animal communities. This should be considered as one of the major mechanisms stimulating diversification of biota as a whole. Thus, the accumulation of biomass within the landscape stabilises the water mesocycle and enhances opportunities for the sustainable use of resources.

This "green feedback" concept can be described as follows:

  1. ENERGY (conversion of radiation energy to chemical energy) - Plants control over 80% of the energy flow through the ecosystem. Plant biomass, to a great extent, determines the amount of water retained on the landscape, and, thereby, stabilises the temperatures and heat budget. (For example, afforestation of grasslands or agricultural areas increases the amount of water retained on the landscape by two orders of magnitude.)
  2. HYDROLOGY - The transfer of water from the landscape to the atmosphere by plants improves the quality of freshwater resources and reduces the probability of catastrophic events by stabilising the water budget at the local, regional, and global scales.
  3. BIOGEOCHEMISTRY - Increasing global plant biomass increases carbon and nitrogen sequestration from the atmosphere, thus providing a mitigating influence to help balance global climate change patterns. Biota are also a major factor in the weathering of the Earth’s crust. The enhancement of biomass will help close biogeochemical cycles and reduce the transfer of nutrients and pollutants from the terrestrial ecosystem to the aquatic ecosystems of lakes, reservoirs, and coastal zones, where the accumulation of carbon and nitrogen in trophic chains occurs.
  4. BIODIVERSITY - Increasing the biomass and diversity of plants in the landscape will increase the biodiversity of animals, which, in turn, will reduce the impact of pest species on wild and agricultural plants.
  5. AGRICULTURAL PRODUCTIVITY - Modifications of the abiotic and biotic factors by plants can help drive climatic factors and biotic interactions toward conditions that can enhance crop quantity and quality. (For example, a reduction in the range of temperature extremes creates more favourable conditions for plant growth; lower wind speeds reduce water losses to atmosphere by evaporation; and reduction of erosion increases the amount of organic matter and nutrients in the soil available for recirculation within the land and water system.)
  6. RESTORATION OF POLLUTED AND DEGRADED LANDSCAPES - Phytotechnologies, or phytoremediation activities, enhance the elimination of pollutants and the restoration of evolutionary ecological processes, energy flows, and nutrient circulation.
  7. BIOENERGY - Higher plant biomass in the system permits the incremental use of primary productivity for bioenergy production on a sustainable basis.
  8. EMPLOYMENT - The restoration and sustainable use of a diversified landscape requires more manpower than large-scale monoculture use. This provides additional opportunities for employment.
  9. ECONOMIC VALUATION AND VALIDATION - The economic valuation and validation of ecosystem services provides an effective framework for the implementation of sustainable resource management strategies.

Given all of these potential benefits, the fundamental question arises: Should we cover the entire globe with tree plantations?

The answer to this question is no. The real goal of ecohydrological and phytotechnological applications is to elaborate the scientific basis for achieving balance and sustainability within ecosystems by the restoration of hydrological cycles and ecological processes, measurable at the basin scale by energy flow and nutrient dynamics. Achieving this goal enhances the capacity of ecosystem to absorb human impacts.

Increasing population creates the need for enhanced ecosystem services, such as water quality improvement, agricultural production, bioenergy production, new technologies, tourism, and recreation. Achievement of this degree of enhancement must be based on an understanding of the underlying biological and biogeochemical processes. Earth evolutionary studies, amplified by studies in the Earth sciences, molecular biology, and engineering, should lead to employment opportunities, improved quality of life, and recognition of the cultural and aesthetic value of the landscape. The first step toward this goal should be to develop predictive models of alternative plant cover development scenarios, under different climatic, hydrological, pedological, and socio-economic conditions. The implementation of phytotechnologies on a global scale should diminish the effect of global climate change and reduce the probability of occurrence of catastrophic events.

Finally, the "green feedback concept" should be viewed as an important opportunity to establish the new technologies to compensate for high rates of population growth and high levels of resource exploitation.


  1. Due to the degradation of plant cover, water has become a non-renewable resource in many areas of the globe.
  2. Plants are important in regulating the energy, water, and nutrient dynamics of the various ecosystems of the Earth. Plant cover is a fundamental condition for making water a renewable resource. Plant cover can be restored through the application of phytotechnologies at the basin scale in order to maximise water cycling through plants.
  3. According to Odum (1989), the ecosystem may be considered to be a cybernetic system because it is been driven by an internal feedback mechanism to ensure maximum biomass, productivity, and efficiency through a series of successional stages. In light of these facts, it has been suggested that control of this process by managing the "green feedback" between energy, water, and plants is crucial for the maintenance of ecosystem homeostasis.
  4. The wide range of physiological performance and adaptive capacity among plant species can serve as an effective tool for the restoration of ecological processes and increase potential for the ecosystem to absorb human impacts.
  5. The main factor limiting progress toward sustainable development is a lack of interdisciplinary scientific co-operation and understanding. As scientists, we often tend to deal with single species, single factors, and individual processes extracted from the surrounding multidimensional relationships in which they exist in nature. In reality, the biosphere is characterised by complex causal interactions. In providing efficient solutions, our understanding of the complex causal relationships and processes which exist in various spatial and time scales - from molecular to basin and biosphere, and from paleologic to prognosis of future processes -  must be improved.

The integration of phytotechnologies and ecohydrology provides the scientific basis for an effective interdisciplinary approach toward the sustainable management of biosphere resources (Figure 4.7).

Fig. 4.7. The integration use of phytotechnologies for sustainability of water resources in the agricultural landscape. (lager image)


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