"Most people occasionally stumble over the truth, but most pick themselves up and continue on as if nothing ever happened." -Winston Churchill
The root cause of global warming, deforestation, starvation, pollution, the mass extinction episode and related issues, is gross human overpopulation. At the first Earth Day, 1970, the population was not yet 4 billion (That number appears to have been achieved in 1974). It hit 5 billion in 1988 with barely a mention. If you want to see the human population growing even as you watch (It just takes a moment, and you will be astonished at the numbers flying by), click on the web address http://www.populationmedia.org/ and glance at the meter to the left as the number heads quickly toward the 7 billion mark. 100 more are added by the time you've read the first paragraph.
There's a biological "overshoot" principle indicating that whether one is dealing with bacteria or elephants, populations, if unchecked, grow beyond the carrying capacities of their environments. A ravaged environment then causes a population to crash. Crashes are generally due to starvation or the buildup or spread of disease agents. With highly intelligent creatures may come psychological impacts, such as increased aggression for limited resources.
Governments have generally been failures at dealing with problems coming from way over the horizon -- when the impact is to occur on someone else's "watch" -- even when those problems are guaranteed and have been carefully explained to governmental leaders. A good example is global warming, the mechanism of which was carefully clarified half a century ago. As seas rise and coastal masses surge into continental interiors .... but why go on when the scenarios have already been described many times and with "leadership" paying absolutely no attention? Alas, ours is a system in which political success is measured by benefits usually in some way monetary and from the standpoint of the earth's life support systems of relatively short term. And why should it be otherwise when our political leaders are nearly all drawn from law schools and the corporate sector?
While it may be easier to blot out mental pictures of ever more teeming hundreds of millions and simply to reach for a drink or to flip on the TV, it would be a kindness to take a moment to think of one's obligations toward one's (potential?) grandchild, and how, at some future point, that grandchild might be considering the future prospects of his or her grandchild.