|dc.description.abstract||Climate change threatens the hydrological and agricultural balance of large river basins, which have sustained civilization throughout history. Although in some instances, certain land-use practices can also pose a threat to river basins, this study highlights land-use changes as a major adaptive tool. Given the great range in system characteristics there will be significant differences in the reaction of differing basins to climate change. Currently, there is no universal approach to how these system changes should be dealt with in terms of adaptation strategy. Before an approach can be developed, the global range of climate change effects and adaptation options must be determined to understand what range of inputs a universal adaptation approach must address.
This study aims to illustrate how contrasting river basins will react differently to climate change, serving as a foundation for the construction of an adaptive approach framework. The study initially conducts a global scale analysis of the effects of climate change on variables such as agriculture, river basin hydrology, vegetation, and development. This results in an analysis of the global distribution of effects relevant to river basin systems. This information was then used as a background for seven river basin case studies representing the range of characteristics such as land-use, hydrology, development, climate, latitude, and geomorphology. Sub issues under the main titles of physical, societal, and future scenarios are investigated to create river basin profiles. A river basin profile is a compilation of predefined information relevant to land-use and climate change. The acquired information is used to determine what threats and adaptation options can be expected in certain regions and basins. In addition, barriers (obstacles preventing adaptation) which exist under those conditions are investigated. Results and conclusions are qualitative because of the small sample size.
Results indicate a variety of combinations and degrees of threat in different continents. Depending on the expected future constraints in physical conditions in combination with the expected societal trends, adaptation barriers were identified which also differed per continent. For example, in North America, the continental US faces large threats of reduction in water resources and agricultural productivity. In Eastern US, there are concerns of threats of increasing discharge and flood. The Mississippi River Basin is subjected to both concerns. There is a conflict in Eastern US between adaptation opportunities leading to identification of a clear barrier. An increase in cultivated land is needed to enhance productivity to counteract losses (in North-central and Eastern US) whereas land is also needed for rehabilitation of wetlands to buffer floods.
Floods are the major concern for the future of river basins throughout Asia. However, in the large areas of Russia that are predicted to experience an increase in agricultural productivity, conflict will raise with the space needed for natural flood buffers. There are also large areas where crop fraction has a profound influence on runoff (and hence discharge) increasing both the negative effects of agriculture in flood regime and the benefit and need for and efficiency of vegetation to buffer floods. Loss of vegetation predicted for large areas will exacerbate flood threats and the corresponding complications.
The threats, barriers, and adaptive opportunities have a large degree of spatial variation in South America and to a lesser degree, Africa as well. Southern Europe faces reductions in crop productivity and water supplies while Northern Europe will likely exhibit increases in both discharge and agricultural productivity. The Rhine River Basin the conflicting challenges of maintaining and improving regulation and navigability and improving ecological continuity simultaneously. This is likely to be a common challenge for most highly populated and regulated river basins. In Australia, reductions in agricultural productivity and water supply are the prevailing threats. In the Murray-Darling River Basin, competition for water is very high between agriculture and crucial wetlands, leading to an adaptation barrier.
In general, higher altitudes and latitudes are predicted to experience increases in both discharge and agricultural productivity upon climate change. Not only will the capitalization on increased productivity be limited by vegetation needed to buffer floods, but also new agricultural practices that minimize erosion will have to be explored. This is because permafrost melt and increased discharge will increase erosion concerns and limit new cultivation. Low latitudes, developing, and arid regions are generally threatened by reduction in water resources and crop productivity. This is often in conjunction with high levels of existing stress on river water resources creating competition for fresh water. Reactions to climate change vary from basin to basin.
The findings of the study indicate great variability of threats, adaptation options, and barriers. The results indicate irrigation efficiency improvement, agricultural shifts, natural flood buffers, and regulation that preserve ecological continuity as the major adaptation tools of the future. The major challenge to the future approach involves balancing compound reactions of a basin often resulting in the conflict between two or more adaptation efforts/options. In addition, efforts are further limited by the allocation of competitive resources such as water needed for both ecosystems and populations. The most illustrative case is the land need for both natural flood buffers and agricultural shifts in the North-Central US. While re-vegetation is likely to be advisable as for a future flood defense, nearby apicultural losses will induce incentives to cultivate the same land. Successful resolution of conflict will require the quantification of needs and adaptation limitations along with the ranking of priorities.
The future framework will have the task of balancing efforts and resource allocation in the face of adaptive limitations posed by conflicting opportunities and high levels of resource competition. Because adaptation efforts and resource allocation have a competitive nature, the limitations they face create a need to determine what actions and resource take precedence over others and to what extent. In the end, there will be a need for sacrifice in order to achieve sustainability. Based on the analysis, the future framework should focus the following principals; quantifying needs and limits, assessing risk, ranking priorities, innovating accordingly.||