It has recently been estimated that the growth in world population has slowed in the past decade. despite this trend, environmentalists remain concerned about the environmental impact of world population, principally

Standard of living is increasing in many developing countries, leading to an increased per capita use of natural resources

Explanation: even if the population decreases however their demand for resources doesn't seem to be going down , according to environmentalists people are demanding more and more of the limited resources such that there is a chance that these resources may not be able to replenish.

As the standard of living increases, people start to demand more from the environment each person possesses resources that can be possessed by two or more people , there is no satisfaction people keep taking non stop.

  b.

there are isolated pockets of farming, generally around rivers and oases, which are used for irrigation.