First things first
There is an old saying: 'Civilised man has marched across the face of the earth and left a desert in his footprints.' (Carter and Dale, Topsoil and Civilization, p.6)
Today, worldwide, on land once rich with natural vegetation, we see deserts denuded of their topsoil, deserts of salt-encrusted soil from years of irrigation, deserts due to widespread deforestation having altered the regional climate. .
The problem from a permaculture perspective has been a lack of design. The solution from a permaculture perspective is to introduce design into agriculture in order to create permanent high-yielding agricultural ecosystems, so that humans can thrive on as little land as possible, thus leaving as much land as possible as wilderness, if necessary helping the wilderness re-establish itself. This visionary global mission is encapsulated in the word 'permaculture', a shortened form of 'permanent agriculture'.