Although biologists have worked for several decades to figure out what makes some plants and animals good 'weeds,' and what makes some habitats more vulnerable to weedy invasions than others, there are no consistent answers.
Invasions are the number-one component of biotic change in the world today.
That task is complicated, however, by continuing shifts in climate, land use, avenues for invasion, and other factors that affect the fate of potential invaders. But not all types of change have equally strong or unambiguous impacts. A number of other global changes, they concluded, have less consistent impacts but still play a role in influencing invasions. The impacts of land-use change are not confined to the land, University of Notre Dame biologist David Lodge noted. Conversion of wild lands to croplands can lead to increased sedimentation and runoff of fertilizers that cloud and eutrophicate waterways, depleting the supply of oxygen, and withdrawals of water for irrigation can change the hydrology of source rivers and lakes.