Humans are causing trees to grow smaller, as big trees are more likely to be harvested. In the same way, elephants are being born in some reserves without their tusks, as this means that they are less likely to be hunted (and therefore, those born without tusks tend to survive better and have more young).
Snails are developing lighter shells, in order to cope with heat better, and swallows are developing shorter wings as this is easier to avoid being hit by cars, are just some of the large number of effects that humans are having on the natural world.
The problem is if these impacts mean that the species is less capable of surviving (do tuskless elephants live as long?). Are humans becoming the primary threat for many species?
If so, we need to change that and fast.
