Desertification of the Earth has its cause in the desertification of the human spirit - from the wasteland of sterile thinking, thoughtlessness and heartlessness, animals are killed, pushed out, tall trees (fir, oak, madrone) are cut down and short trees planted (pear, plum, apple), then the short trees cut down and grape vines planted, then the vineyards are bulldozed for subdivisions.
Rivers channeled, dammed, the water taken to irrigate, to pipe to thirsty subdivisions and to water the livestock, soon to be deadstock. Then periodically a natural drought cycle returns and the land is no longer flexible and diversified enough to withstand several years of lowered rainfall - crops wither, lakes dry up, the ground hardens and cracks, fires and insects ravage the 2nd and 3rd growth forests (whereas the old-growth forests had seen many droughts, fires and plague come and go, and passed down the knowledge of how to survive through the seeds of its cones).
Step by step the land is turning into desert, eventually becoming uninhabitable to the residents, who abandon their unproductive and bone dry rockpiles for greener pastures. Witness the stone remains of once-flourishing Tsaparang in Tibet or the Sahara rock drawings of the once-abundant flora and fauna of that region. Read descriptions of the island of Ireland when the first people arrived there: endless forests, lakes, numerous large animals such as elk and bears. Or read very similar descriptions of the Santa Clara Valley of about 1780. And now photographs record the decrease in biological mass as it happens in the rain forests of Madagascar, Borneo, Brazil, and Zaire.
The way to replenish the Earth is by refertilizing the heart with ancient wisdom, the wisdom of the Buddhas, the wisdom of nature. The Book of Genesis records that God gave man dominion over nature and all its plants and animals - the 6000 years since that was written have provided ample evidence for man's misuse of that power of dominion. Therefore turn from being a steward of death to being a steward of life. Become a feral human. "Feral" means animals who were once under the protection of civilization, but have somehow escaped and returned to the wild. Some men are able to do the same, difficult though it is.
By coming to understand the depths of your own mind, its thoughts, impulses, desires and habits, you may then be able to loosen the bonds of civilization, get away from the breeding pens called cities, and in the meditative state called "samadhi" come to know the ecstatic state of the Buddha within. Stop the indulgence of habits and thought patterns, give up anger; there is an adventure ship leaving from every port every moment - cross the great ocean of afflictions, get off on the far shore, set out on a trail into the wilderness, the Bodhisattva Path of kindness, insight, light and heat.