Aquatic systems and water security in the Metropolitan Valley of Mexico City
In megacities water quantity and quality are threatened by complex and interrelated processes caused by population growth, land use change, unsustainable agricultural practices, deforestation, erosion, destruction of ecosystems, lack of planning, laissez-faire policies, unsustainable water management, political conflicts, and increasingly also by the impacts of climate change. In the Metropolitan Valley of Mexico City (MVMC) located in the high plateau of Mexico City and on former lakes, the dry out policies during the last 300 years have been counterproductive, causing scarcity, pollution, health and environmental problems, subsidence and water conflicts, particularly affecting social vulnerable people. Megacities require an integrated management of water and aquatic systems — integral water resource management, rainwater harvesting, maintenance and replacement of infrastructure, restoration of ecosystems and urban planning. This implies investments and a water culture including a transparent administration and peaceful negotiation of conflicts regarding concessions, access, and reuse of water allocation. Socio-political and environmental processes are complex; besides technical factors and ecosystem recovery, socio-cultural changes must transform human settlements and power structures.
Water security and national water law in Mexico
BackgroundThis article develop analyses water security in Mexico, a country where global environmental change requires social, political and economic actors to protect natural resources and ecosystem services in order to reduce the tension between anthropogenic demands and natural availability. The paper asks: How can overexploitation and inequality in the access and control of water be assessed using an integrated model of water management and how could the existing water resources in each river basin and aquifer be sustainably distributed by a new National Water Law that would encourage participation in order to overcome the conflicts over access to and control of water?MethodsWith a model of integrated water management the article reviews the current use of water among different social and production sectors.ResultsAgriculture still consumes 77 per cent of the water, especially in the arid north, an area greatly affected by climate change (CC). Industry uses ten per cent and domestic users thirteen per cent of water. The growing megacities are also overexploiting their aquifers, producing subsidence and water pollution together with changes in land use, thus reducing water infiltration into the aquifers during the monsoon. Regional and temporal water stress is further aggravated by unsustainable production processes, where mining and agribusiness hog the water needed by indigenous people and small farmers, forcing them to migrate to the urban centres or illegally to the US.ConclusionsWithin this arena of conflict in the field of water management, the article offers several guidelines for a sustainable and participative National Water Law. Food security, including dignified life conditions for the small-scale farmers in rain-fed regions affected by CC, could be achieved with small scale irrigation system in the Southeast of Mexico, where water is available for a second crop. Their sustainable agriculture and preventive management of water pollution by organic agriculture are central activity for conserving and restoring the natural condition of water infiltration. Without an integrated water management, reduction of soil erosion, early warning and resilience-building among the exposed people, Mexico will not reduce the existing and future threats related to global environmental change and particularly to CC.
Palaeocarpinus (Extinct Betulaceae) from Northwestern China: New Evidence for Paleocene Floristic Continuity between Asia, North America, and Europe
Spiny-bracted fruits of Palaeocarpinus Crane, a genus of Betulaceae previously known only from Europe and North America, have been discovered in the Paleocene of Altai, northwestern China. The fruits are found in association with abundant Corylus-like foliage and staminate catkins containing Corylus-like pollen. Because of problems distinguishing leaves of Corylus from those of extinct betulaceous genera, we place these leaves in the genus Corylites Gardner ex Seward & Holttum. The fruits, staminate catkins, pollen, and leaves from Altai were probably all produced by a single species. Palaeocarpinus orientalis is nearly identical in its morphology to Palaeocarpinus joffrensis from the Paleocene of North America except in the more rounded primary bracts of the associated staminate catkins. The species is less similar to Palaeocarpinus laciniata from the Paleocene of southern England.