<span>Trees grow below or above the timberline, or tree line, depending on the environmental conditions present. Alpine tree lines are common near or on mountains and mountain ranges. The weather above the timberline is too cold and possibly too dry for trees to grow and take root. Desert tree lines are common in and near deserts. The soil is too dry for the trees to take root and get the water and nutrients they require. Desert-Alpine tree lines are environments where the elevation is too high and the soil too dry to foster tree growth.</span>
Because its in the middle or center of the area
Adam Smith theories promote individualism in the sense that they state that, when each economic agent (households, business, or public entities) pursue their own interests selfishly, the outcomes generated by their economic activities will optimize the social welfare.
The incentives behind working for the own profit are much higher, and make individuals more productive and more sensitive to mistakes, therefore they are keen on improving their practices constantly. In turn, the incentives of working for the common interest are more vague, and such situations lead to sharp productivity declines. It is more likely that societies with greater productivity are able to produce efficiently enough goods and services to cover the needs of all its citizens. Therefore those societies end up maximizing the social welfare. These are the main arguments which support the invisible hand principle coined by Adam Smith.
