Rooftop gardening is growing in popularity in the concrete city. City dwellers are planting vegetables, fruit, flowers and all kinds of plants on their roofs. They are getting fresh food, and the temperature of their roofs is gradually changing too. The question arises: do rooftop gardens really play any part in protecting the ozone layer?

The ozone layer lies mainly in the stratosphere, where ozone molecules absorb the sun's harmful ultraviolet rays. Without its protection, people could suffer skin disease and eye problems, and crops and biodiversity could be seriously affected. The main cause of ozone destruction is man-made chlorofluorocarbons and other harmful gases. Yet every plant on Earth contributes indirectly to keeping the atmosphere safe.

In mechanised cities in particular, rooftop gardens contribute in several ways. First, plants absorb carbon dioxide and release oxygen. Less carbon dioxide reduces global warming at least somewhat. Rising temperatures and global warming weaken the ozone layer, so rooftop gardens indirectly help control temperature.

Next, rooftop gardens reduce the city's "heat island" effect. In a city like Dhaka, concrete, tin and paved roads generate excess heat that makes the environment hotter still. Plants reduce this heat, lowering the city's temperature, and work tirelessly to keep the atmosphere normal.

Rooftop gardens also absorb some air pollution. In Dhaka, vehicle smoke, industrial emissions and dust from construction together make air pollution dire, and much of this pollution has a negative effect on the ozone layer. Leaves and stems trap dust and fine particles, keeping the environment somewhat cleaner.

Research shows that greening on a large scale is very important for keeping the urban environment in balance. For example, according to research from the University of California, Berkeley, green roofs or rooftop gardens contribute to protecting the ozone layer.

Dhaka now has small and large gardens on the roofs of hundreds of buildings. The more there are, the greater the collective effect. No single rooftop garden directly repairs the ozone layer, but together such initiatives are playing a part in protecting the global environment.

Today is the International Day for the Preservation of the Ozone Layer. The fight to protect the ozone layer does not depend only on international agreements or major industrial policy; every tree you and I plant, every green initiative, contributes too.

Rooftop gardens, then, are not just for beauty or food; they are also partners in protecting the environment. Let us become aware and take action. City dwellers' small green steps could be a big strategy for saving Earth's blue sky.

Source: Jagonews24. First published in Bengali on The Agro News.