[imesh]

Sort of off topic: One of the more frustrating things about going out in nature where I live at least, is seeing the pattern of invasive plants over and over again. I can identify every plant in my area, an area that would have been full of thousands of different trees and bushes now has repeating landscape of about two dozen different plants.

[ratacat]

At some point in time, every plant was invasive.

[erikpukinskis]

No, invasiveness is a quantitative measure. A plant can force other plants out, or it can coexist. The amount of net pressure on other species dictates whether a plant is invasive. A Eucalyptus and a Live Oak will both use the same sunlight but the Eucalyptus will lol everything underneath it.

Also, it is true that sunlight is a fixed resource, but the earth is not 100% covered, even in mature forests. There are disturbances everywhere that can be moved into and stengthening the ecosystem.

There are also resources which are not sunlight. The resource competition is so multidimensional and open that you cannot conceive of life as a zero sum game. Not yet anyway. Maybe in another billion years of evolution we will be at the point where every movement is an invasion.