 We could not plant enough trees. There's not enough density that we could plant trees in a city to reduce the carbon dioxide in the city. And I will point out that in a city, the carbon dioxide level in the atmosphere is typically 10 to 20 times that of the global average. And people don't die. It's not a pollutant like some people claim. But the best thing you can do for cities is to change the albedo. Now, the albedo is what the reflectivity of the Earth is.