GMO agriculture will probably save the world in this century. But in the developed world, where few people are haunted by the specter of famine, people are free to fetishize heirloom tomatoes and worry about the provenance of what sits on their dinner tables.

In fact, the early demographer Thomas Malthus believes that the only way the human population would ever check itself was by running headlong into a disaster, like a pandemic or famine. Sometimes we get so frustrated with the slowness of human political processes that we wish a giant flaming rock would solve the problem for us.

The fact is that humans have been shaping the genetics of what they eat for thousands of years. Genetic engineering simply speeds up the process that used to take generations. Preventing people from getting things like golden rice or disease-resistant cassava destroys human life, and does not spare the environment in any way.

Amphibians are dying out like crazy, and frogs and salamanders may be largely extinct by the end of the twenty-first century. Imagine an animal that begins its life in the water, but ends it on land - already, that's pretty weird. But, also, a lot of them are incredibly tiny and look wildly improbable. They have funny little toes, they stretch their throats into weird bubble shapes when they croak, and some of them are poisonous to the touch. I think kids from the twenty-second century might mythologize amphibians the way kids today mythologize dinosaurs.

If we return abruptly to a Miocene-like climate, it's reasonable to think that we would experience a lot of extinctions, and maybe even a mass extinction in the long term. Would the life on Earth be radically different? Of course we can't say for sure, but I think a lot of it would look familiar. Like a lot of people, I worry a lot about whether marine mammals would survive, especially whales. Ocean acidification is one of the major killers in climate change events, and that makes the ocean a very inhospitable place.

Sometimes it's hard to take everyday concerns seriously when you think about vanished ecosystems that existed 300 million years ago and were eradicated by giant explosions. My goals haven't changed, because my goal has always been to save the world!

We have converted huge swaths of land and ocean into human habitats where we live and grow food and harvest energy. But there's been a sea change in the past century.