The big picture of marsh loss

摘要

The widespread use of fertilizers has greatly altered global nitrogen and phosphorus cycles, which are now dominated by anthropogenic rather than natural processes1'2. A substantial portion of fertilizers are ultimately transported into rivers and to the sea. One consequence of this increased nutrient supply is the proliferation of'dead zones' at the mouths of the worlds rivers - areas where the decomposition of fertilizer-driven algal blooms has used up most of the oxygen, leading to the death offish and other large organisms3. Wetlands could provide a solution to this problem, because they chemically transform nutrients as they flow from land to sea. In particular, coastal salt marshes transform nitrate, the most abundant form of nitrogen in fresh waters, into nitrogen gas, thereby limiting the amount of nitrogen reaching the ocean4.