Instrução: a questão refere-se ao texto abaixo:
Water for Our Future
Fresh water is arguably the world’s most precious resource. Yet in all corners of the globe, shortages and inadequate access to sanitation persist. Rivers are fragmented by dams, choked by chemicals, threatened by climate change, depleted by irresponsible businesses and industries that don’t manage water wisely, and polluted by toxic runoff from cities, factories and farms. We can’t solve these challenges alone, and thankfully, we don’t have to. Although there are many millions of miles of water on the earth, it is thought that most of this total is salt water or ice, and therefore not usable for human needs. Also, we cannot use more than one-third of the water that falls from the sky. The other two-either disappears back into the air, or is used by plants, of flows into the sea or under the ground. Indeed, some of the places where man formerly obtained fresh, clear water are disappearing. Along the coastline of the United States, humans have used so much of their natural supply of water that sea water is very slowly taking the place of the clear water as it is used. This loss of good water cannot continue. More and more people are demanding more and more clean water every year. It has been figured that the modern city family uses six times more water today than yesterday’s farm family did, when wells were the main source of water. Where will we get the water that our increasing population requires just to stay alive? What can we do about our water supply? The only answer is that we must learn to reuse water and the main difficulty to do so at present is the problem of water pollution. We are being attacked on all sides by water pollution of all types from all kinds of sources. The time has now come for man to make his environment his friend, not his enemy. Water is a local issue, but addressing water resource management challenges requires global solidarity as well as regional, national and local actions. Something must be done, and must be done on a large scale. However, one great problem of the crisis is that decisions must be made today, before the need has become generally apparent, to prevent adverse effects that are projected to occur in a more or less distant future. There is wide spread agreement that humanity should start securing and improving its water resources in order to adequately deal with the other environmental problems that may arise.
(Adapted from: The North American Regional Process event for the 7th World Water Forum, Karin Krchnak, Director Freshwater Program, May, 2014, Washington, DC)
According to the text, “it is thought that most of this total is salt water or ice”, it means that:
