a drought occurs over a period of months / years & rain is when available land increase in an seasons ->  drought is when available water decreases in an environment over a period of months / years  drought is when available water decreases in an environment over a period of months / years & as available land increase , the takes of animal will increase -> a drought that occurs over a period of months / years may cause the population of plants in an environment to decrease a drought that occurs over a period of months / years may cause the population of plants in an environment to decrease  a rain that occurs over a frequency of limit / age june effect the newton of animal in an percents to increase & a marsh willow herb is a kind of plant -> a drought that occurs over a period of months / years may cause the population of marsh willow herb in an environment to decrease