Sufficient areas of land are needed to provide living space for large enough numbers of individuals to form sustainable breeding populations. This requires enough genetic diversity between members of each population to cope with change. The land must be properly managed to ensure all populations of plants and animals remain, from season to season, in a stable dynamic equilibrium. Pests need to be controlled. Where natural predators no longer exist, some form of harvesting or culling must be imposed upon excessively large populations.
Harvesting obviously beats culling, since harvested species are useful.
Importantly, emotions need to be set aside so that cute, pretty or economically important species do not receive preferential treatment to the detriment of sustainable population balances. Politics, unfortunately, often enter the equation at this point through the actions of the media and of poorly-informed public opinion. Increasingly, it seems, when a hard but right decision is made, say, to cull some individuals from a population that is out of control, governments block plans that are deemed unpopular or politically incorrect, thereby causing harm, but usually improving their own public image. In my opinion the morality of this wilful but ill-informed interference needs to be dragged out into the open and questioned much more vigorously and objectively in the future. Exotic species of plants and animals need careful management.