When fire-fighters arrived to extinguish the fire, that had engulfed the home of a 66-year-old woman, Elise Inversin, on the French island of Corsica, she told them to leave her house and save a neighbouring 900-year-old Mastic tree because the house could be rebuilt. Inversin travelled from Corsica to Paris to receive a ‘Tree of the Year’ prize on behalf of her beloved Mastic tree to mark the United Nations’ International Year of Forests in 2011.

Unfortunately, in our country, both young and old trees are cut indiscriminately. It seems as if the civic agencies are not aware of the environmental, ecological, social, physical and aesthetic benefits the trees provide as well as being highly instrumental in minimising the impacts of climate change and sea-based tsunami episodes.

A fully grown tree provides two to three cubic metres of timber, produces 4.6 tons of oxygen and absorbs 6.3 tons of carbon dioxide every year, and produces 55kg of organic material, fodder and firewood annually. Air purification through technical extraction of carbon dioxide would cost $102 a year.

A mature tree absorbs 30,000 litres of groundwater, acting as a mini-reservoir delaying surface water runoff and preventing the damage caused by rains in terms of soil erosion to a large extent.

The tree’s direct functions are supplemented by a series of indirect ones. The organic droppings from the tree break down to fertile humus in three years, through the action of soil organisms. This means that the tree annually produces 40kg of bacteria, 40kg of fungi and algae, 17kg of earthworms, beetles and ants and 3kg of other insects; all of which help in the decomposition process.

Around half of the present level of air pollution is absorbed by woodlands. A healthy tree filters up to a ton of dust and obnoxious substances each year and when the amount exceeds its level of tolerance, the signs of damage are the most effective of all alarm systems. The leaves also absorb toxic and radioactive substances to a certain degree.

Trees provide many facilities such as shade, rain protection, breathable air and orientation. The forest provides a habitat for wild animals and birds, and produces mushrooms and berries independently of human cultivation.

A tree’s protective function against wind and water erosion is outstanding. If the protective woodlands in the mountainous regions had to be replaced by technical constructions to prevent landslides, avalanches, etc., the cost would be exorbitant. Trees also prevent the banks of rivers and lakes from being washed away. One of the major causes of devastation caused by floods in Sindh in 2010 and 2011 was loss of tree cover.

Wooded regions have a high recreational value and therefore are invaluable assets for the tourism industry. The tourism potential is supplemented by their ability to produce biologically beneficial substances such as volatile oils, turpentine and aromatics.

Trees contribute to the agricultural sector by improving soil by creating a beneficial microclimate for an increased yield. Trees also maintain land values because their presence shows that the land is fertile. On a unit hectare basis, the cost of a land with trees is nearly 10 times greater.

Even a sick tree has an important function. It forces decision-makers to take measures against air pollution from which not only trees, but humans too suffer. Impairment of the health of the human population has economic impacts ranging from the cost of medical services to the temporary loss of production personnel. In a major urban centre, trees define the quality of life and the moral values of the population.

Trees are ‘carbon sinks’. They remove carbon dioxide from the ambient air, preventing global warming. Trees also remove other major air pollutants including sulphur dioxide, ozone, nitrogen oxides and particulates that cause respiratory problems.

Trees are a renewable source of energy because of the wood and biomass products. Trees may help in reducing expenditures incurred on electricity. For example, the shade provided by trees keeps a house relatively cool which lowers the air-conditioning requirements.

Despite the major benefits of trees, Karachi seems to prefer a tree-less environment. Mai Kolachi area, once green, now has no tree cover. If Karachi’s environment is to be improved, steps need to be taken to grow more trees and prevent the wasteful habit of cutting of trees.

F.H. Mughal