The Coupled Carbon-Water Cycles: Imposing the Atmospheric Constraint

水对人类社会具有独特的重要性，而二氧化碳(CO2)是最重要的长寿温室气体。二氧化碳是人类燃烧化石燃料时排放的，并参与控制其在大气中命运的碳循环。碳循环和水循环形成了一个紧密耦合的系统。例如，植物通过气孔开放的光合作用吸收二氧化碳，不可避免地会通过蒸腾作用导致水分损失。此外，寻求从大气中隔离碳或保护水资源的管理做法必须考虑对碳循环和水循环的影响。

Water is of singular importance for human society and carbon dioxide (CO2) is the most important long-lived greenhouse gas. CO2 is emitted from human combustion of fossil fuels and participates in the carbon cycle, which controls its fate in the atmosphere. The carbon and water cycles form a closely coupled system. For instance, photosynthetic uptake of CO2 by plants through stomatal opening inevitably leads to water loss through transpiration. Furthermore, management practices that seek to sequester carbon from the atmosphere or preserve water resources must consider the impact on both the carbon and water cycles.