Tielbörger et al. (2010) examined the severe water crisis in the eastern Mediterranean to determine productive water and land allocation schemes. They defined water productivity as the full range of services provided by landscapes per unit of blue (surface) and green (in plants and soil) water instead of economic returns, measured in GDP, obtained from using a certain amount of fresh water. That is to say, water-use and land-use management are inseparable. Their studies suggest that, in Israel, certain landscapes provide high returns in the form of ecosystem services for little additional input of blue water. Rangelands appeared to be minimally affected by climate change, making them ideal for adaptive land management. — Madeleine Busacca
Tielbörger, K., Fleischer, A., Menzel, L., Metz, J., Stemberg, M., 2010. The aesthetics of water and land: a promising concept for managing scare water resources under climate change. Philosophical Transactions of the Royal Society A 368, 5323–5337.
While precipitation is undoubtedly decreasing throughout the Mediterranean basin, the Jordan River basin is located in an especially water-stressed region with record lows in per capita water availability. This water crisis in Jordan can be attributed to low natural water availability, a rapid increase in the demand for water due to population growth, and climate change including an increase in temperatures, decreasing annual precipitation, and an increase in the occurrence of climatic extremes.
Tielbörger et al. developed the GLOWA Jordan River project, an approach to water management integrating the physical basis of water supply and the water demand within social and economic boundaries. The model is dependent on their modification of the traditional meaning of water productivity described earlier. Previous models underestimate the demand of water because they ignore the fact that there are two types of water involved in productivity: blue water in aquifers, lakes, rivers, and wetlands, and green water which is stored and recycled through plants and soils. The only source of green water is precipitation, while blue water can be managed via technology, wastewater treatment, desalination, and virtual water trade. Integrating green water into the model is crucial since green water accounts for more than 80% of the global consumptive water use for a wide variety of crops, as well as playing a major role in desertification.
Tielbörger et al. tested three main hypotheses in Israel: that the recreational and aesthetic value of a landscape may be much larger than returns from provisioning services, that water productivity of rainfed landscapes may be maintained under climate change and may exceed that of irrigation water-dependent land-use schemes, and that water productivity of irrigated agriculture will drastically decrease under climate change, owing to a marked increase in water demand.
Results showed that returns from land use, especially from rangelands, are not necessarily affected by climate change when taking non-market values, such as landscape value, into account. Tielbörger et al. disagree with previous studies that suggest humans and nature are competing for water. Rather, the authors suggest that when considering the complete range of possible services provided by agro-ecosystems, society may benefit from the protection of green water flows. However, water security will be compromised under changing climatic conditions if high irrigation demand continues to be fulfilled. Ultimately, the results support the authors’ confidence in a blue-green approach being the key to water sustainability and to land management optimization.