Author of How To Save Our Planet: The Facts
Professor of Earth System Science at University College London

I think the most important thing is realizing how much impact humans have had on the planet. For example, did you know that we move more rock and sediment than all the natural processes put together? We also have created enough concrete already to cover the whole world in a layer that's two millimeters thick, and that includes the oceans. We have also created and make something like 300 million tons of plastic every single year, which we know ends up in our rivers. It ends up in our oceans. And we've also found that microplastics have been found in human blood. So this is the impact we're having all around the world. We've also cut down 3 trillion trees, that's half the trees on the planet. We have doubled carbon dioxide in the atmosphere. We've increased methane by about 150%, which has led to a warming of the planet of about 1.2 degrees Celsius. And If you weigh the land mammals, 30% of that weight is us humans. There are 8 billion of us, and I have to say a few of us could lose a few pounds, but 67% of that weight is our livestock. And just 3% is those wild animals. So in less than 5,000 years, we've gone from 99% being wild animals to less than 3%. That's how much impact we humans have had on the planet.