Dry,drought-prone regions of the world produce nearly a third of the global food supply.and many of the crops in these regions are in danger of going thirsty not only because the soil they grow in contains too little water,but because it contains too much salt.
Salt is a natural part of soils everywhere it forms from minerals weathered out of rock-but in wet climates,most of it gets dissolved by percolating rain and carried down to the groundwater below.In dry climates,on the other hand,percolating rainwater rarely makes it that far most of it gets soaked up by the deep roots of native plants,causing its salts to precpitate out and gradually accumulate in the soil below.
盐本就是土壤中无处不在的一部分，它形成于岩石风化出的矿物质，但在常温气候区 大部分的盐会被雨水融化，并随雨水迁移至地下水中，在气候干旱区则不然 雨量少 渗透不了那么深大多数水分被土生植物的深层根系吸收，导致盐分沉淀 逐渐在土壤中积聚。
This saltly layer isn't a problem as long as both the plants and the water table stay where they are,but when native vegetation gets swapped out for shallow rooted crops,more rainwater makes it all the way to the groundwater,causing the water table to rise.
如果植物和地下水层都坚守原地 那么盐层并不成问题，但是当原生植被换成浅根作物时，多出来的雨水一路渗透地下水中 导致水面上升。
On its way up,it dissolves the salt deposit,bringing salty water to crops' roots.And here's where the hydration problem comes in:individual molecules of salt are a lot bigger than molecules of water,so they get stuck in narrow junctures in plants' plumbing and cut off their water supply.
在此过程中 雨水溶解了沉积的盐 将盐水带至植物根系，于是水合作用问题来了：单个盐分子比水分子大多了，于是它们卡在了植物输水管道的狭窄处 阻断了水分供应。
At best,a plant that can't hydrate properly grows slowly;at worst,it dies.And irrigation just exacerbates things;irrigated water comes from rivers and lakes and is slightly saltier than rain,so it adds salt directly to the soil while speeding the water table's rise.
情况好时 一株无法水合的植物会生长缓慢，情况不佳时 会死掉。而灌溉会使情况更糟：灌溉水来自河里或湖里 盐分比雨水略多些，所以它除了增加土壤盐分外 还加速了水位的上涨。
We humans have run into this problem before historians believe salty soils contributed to the fall of ancient Mesopotamia.We're seeing some effects today,too:as much as one quarter of all irrigated dry farmland on Earth experiences reduced yields due to salt.But even without additional water,groundwater comes up fast:for example,when forests in southwestern Australia were converted into non-irrigated farmland,it took just 12 years for the water table to rise 18 meters to the surface.
人类很早前就开始设法解决这个问题历史学家认为古美索不达米的衰弱与土壤盐化有关，如今我们依然深受其害：地球上1/4的灌溉旱田正因盐分而减少产量，但是即使不浇水 地下水上涨速度依然很快：例如 在南澳大利亚森林转变为无灌溉田后，仅仅12年地不水位就上升了18米。
One way farmers in dry regions deal with this problem is by periodically flushing their soils with enough freshwater to remove the salt.This works-temporarily-but requires a lot of water,sometimes more than is used on crops over an entire growing season.
A better option is to plant thirsty,deep-rooted trees and shrubs,which can soak up most of the percolating water and reverse the rising water table,In Australia,native trees planted amongst conventional crops slurped up so much water that the water table fell 3 meters in a decade,taking its load of dissolved salts with it,And farmers in Uzbekistan achieved similar results by swithching back and forth between crops and native shrubs every few years.
更好的选择是种植耗水且根深的树和灌木，它们能吸收大部分的渗透水 降低上涨的水位，澳大利亚 在传统作物间种植的本土树种消化了大量水分 令地下水位在10年里下降了3米，且地下水将盐溶解带到了地底深处。乌兹别克斯坦的农民通过每隔数年 轮流种植作物和本土灌木的做法取得了相似的效果。
But regardless of whether we alternate them spatially or temporally,we will most likely need to rely on drought-adapted native plants to help preserve the large swaths of dry,increasingly-salty farmland that produce a third of the world's food.
Because in this case,if we salt our food before we taste it,we might not get to taste it at all.