Discussing the 50/50 concept with people often requires clarification of what it is trying to achieve. Saving half of the Earth’s natural habitat is not intended to save every single species in existence today, nor bring about some kind of utopia. What it is intended to do is leave enough un-exploited habitat of all kinds, not just the places people don’t want, to continue to support natural bio-diversity and evolution. Preservation of existing species should become much easier if they have significant contiguous habitat space in which to live, but the main point is to give the whole biosphere space to “do its thing” without intense, close range human interference.
At our present level of technology and economy, homo-sapiens is capable of exploiting most of the planet, and we are rapidly expanding to do this. The areas where man has done this already for thousands of years, such as the Fertile Crescent, don’t look like a great model for a sustainable world. Converting large swaths of homes, farms, factories and businesses to preserved parkland sounds impossible, but it has been done in some large scale areas like the 82 square miles of Mammoth Cave National Park and 2357 square miles of Everglades National park.
Asking people to give back 1/2 of all the Earth’s land to nature is bold, but asking nature to give 100% of the Earth’s surface over to exploitation is foolish. Management through complex education, politically motivated laws and enforcement is difficult at best, and often unsuccessful. What has seen dramatic success is management through exclusion, such as marine and terrestrial reserves. If we acknowledge that some nature reserves are necessary, and that human population has to have some maximum limit, it would ultimately be self-serving for humanity to limit itself well short of whatever “critical collapse point” of exploitation there is.
This is not to say that the preserved areas would become some sacrosanct zone of total human exclusion – ecologists would still study them, identify bad trends like elephants decimating vegetation, and take appropriate corrective action. On the other hand, questions like oil and gas exploitation, conversion to agriculture, hunting, fishing, wind and solar energy collection farms, dumping, and urban development would be met with a resounding NO in the preserved areas – not studied, justified, politically bartered, regulated, mitigated, exchanged or restored, simply preserved. It’s only half of the Earth, we don’t really need it to survive, thrive or compete, but nature does.