I first read about this book and the ideas therein in the near-future environmental novel Ministry for the Future by Kim Stanley Robinson. In Ministry, one of the major trends that happens is wildlife corridors between and among major national parks, resulting in a “re-wilding” of rural and residential areas that had previously separated parks into tiny wildlife islands.

I was intrigued, so I got the book. And right in the first chapter, Wilson says, “I’ve written Half-Earth as the last in a trilogy…”. So, that got me to digger deeper into Wilson’s body of work first; I read The Social Conquest of Earth and The Meaning of Human Existence, and thought hard about them, and wrote about them. They were both really strong, thought-provoking works. Wilson is an entomologist who has specialised in ants and termites, and his study of these social animals has given him special insight into the place of humans in the Earth’s environment.

Half-Earth turned Wilson’s thoughts to a particular topic: the biodiversity crisis and how to mitigate it. Non-human species on earth are experiencing extinction at a 100x or 1000x level compared to previous centuries and millennia. The Global Assessment Report on Biodiversity and Ecosystem Services estimated that more than 80% of wild mammal biomass, 40% of amphibians, a third of corals and fish, and 10% of insects have been lost in the last 50 years.

Wilson outlines how biodiversity is under attack, and what our options are for slowing its decline and eventually restoring it. He explains how species are threatened by HIPPO — habitat loss, invasive species, pollution, human population, and overharvesting. He discusses what level of biodiversity is important to maintain healthy ecosystems, and how ecosystem health is measured.

He gives some careful, emotional descriptions of species on the brink of extinction, like the rhinoceros, and species that have crossed that line, like certain freshwater shellfish of North America. He talks about the tragedy of when any species disappears, and makes the reader face the prospect of thousands or even millions of species disappearing by the end of the century.

One very interesting part of the book is his discussion of how little we actually know about the natural world; how many species we believe exist but which have not yet been catalogued; and how meticulous and exhausting the work of naturalists the world over is in finding, identifying and naming species. It’s a really compelling view of how small our understanding of the natural world is compared to the complexity that we know is there.

Wilson has a particularly scathing rebuke for futurists and technologists who imagine an “Anthropocene” era in which ecosystems are engineered by humans from species in different parts of the world. Stewart Brand gets a particular call-out for hubristic, too-smart-by-half promotion of architected environments. According to Wilson, we simply don’t have the skills nor the knowledge to manage the level of complexity of even temperate bioregions, where tens of thousands of plant, animal and fungus species can occupy the same square kilometer, let alone the equatorial tropics, where the complexity goes up even higher. Ideas that we can do as well or even better than millions of years of evolution in architecting ecosystems interoperable plant and animal species is simply unreasonable. Our only option is conservation and restoration of ecosystems that already exist.

This is where Wilson delivers his major thesis: that we have to reserve 50% of the Earth’s land and 50% of the Earth’s water for nature conservation and restoration. These numbers come from one of Wilson’s major contributions to ecology: the recognition that big, connected areas of reserved nature preserves are much, much better at protecting biodiversity than small, isolated areas. His math shows that if we can reserve half of the Earth, we can save 80-90% of existing species.

Where the book falls short, I think, is in providing concrete steps to getting to that 50% reservation. What are the steps to get from our current level of conservation (15% of land, 10% of water) to that full 50%? What’s the potential timeframe? What are some good techniques for getting there? How do we rally a biodiversity movement around that number?

I found Douglas Tallamy’s books on biodiversity like Bringing Nature Home really accessible because they gave a direct method for an individual like me to participate in restoration ecology. Wilson’s book is a better clarion call for action on conservation and restoration, but I think it lacks a description of potential solutions.

And it doesn’t really paint a picture of what a Half-Earth world would be like. What does agriculture look like? How are cities different? What about transportation? What does it feel like to have a web of nature preserves interwoven with our residential, commercial and industrial properties? I think it’s an interesting and beautiful imagined future, but it needs more elaboration than Wilson gives it.

All in all, I think this book was worth the wait. I’m glad I got to it, even if I had to take the long way around. I’m interested to read more about the topic, and to see what I can do to contribute to a half-earth future.

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