After gasping for breath for almost a week under the most unusual dusty haze in the middle of summer, city residents learned that the national capital was to lose more than 16,000 full-grown trees from the heart of south Delhi. The trees will be axed to make way for constructing high-rises in the seven leafy neighbourhoods that once housed government officials.Already the second largest urban sprawl in the world, Delhi and the adjoining National Capital Region (NCR) towns are a perpetual construction project, with more residential flats, roads, flyovers, pavements, Metro lines, shopping malls and offices coming up in every possible vacant space. While it loves to build, NCR has no concrete plan to deal with its construction waste. The capital generates at least 4,000 tonnes of construction debris every day. But it has only two plants to process half of this discard. The rest is dumped anywhere, including the Yamuna floodplain.In Gurgaon and Faridabad, dumping of concrete into the Aravalli continues unabated despite court strictures. Soil erosion, concretisation and deforestation have turned one of the world’s oldest mountain range, which for ages has arrested the eastward march of the Thar, into a “rocky desert” itself. “The denuding of forests is advancing the desert, particularly in gap areas with increasing intensity of dust storms,” warned a report by the Wildlife Institute of India last year.Following a nasty spell of squalls, which has claimed several lives since May, scientists have warned that such storms will be routine now that temperatures are shooting up and rain becoming scarce.Old-timers are left wondering since when the seasonal “aandhi” — the hot, dry wind blowing from the Thar that was part of the Delhi legend — become so dangerous.Dust storms can be disruptive and trigger health problems. But in the NCR, they have assumed deadly proportions mainly because we are no more dealing with the seasonal desert sand alone.Today, much of Delhi’s ‘earth’ is made of construction dust and building material – sand, cement, mineralised quartzite (popularly known as the Badarpur soil) or finer concrete. This construction waste is not only on the ground we walk on but also in the air we breathe.According to the latest air-pollution source appropriation study by IIT-Kanpur, soil and road dust can contribute about 26% to PM10 and PM2.5 in summer. Experts say that the dust aerosols are now routinely getting mixed with the pollution ones. With sand blowing from the west, comes dust from construction zones stretching as far as Rajasthan.While laws against dumping have to be strictly enforced, Delhi and NCR towns also need better site management. Travelling out of Beijing by train recently, I could see even the most distant construction sites in the hinterland covered with tarpaulin sheets and fine nets. Builders in the NCR make no such effort and enforcement teams get active only after pollution alerts are sounded.In such a mess, Delhi’s surviving trees, themselves covered in layers of construction dust, are our best ally in the fight against air pollution. That’s why the plan to axe more than 16,000 of them is plain suicidal — just as the idea of compensating the loss by planting saplings is ridiculous.Look at China for a lesson. Having felled trees that acted as a buffer between the Gobi and Taklamakan deserts and its cities, China has been trying to revive its degraded drylands by growing a “great green wall” and already planted 66 billion trees under the Three-North Shelterbelt Project since 1978.Yet, it will take China at least another three decades to have a green wall stretching 4,500 km along the edges of its northern deserts in place by 2050. That too only if the afforestation project can significantly reduce the mortality rate of the planted trees.Planting another Great Green Wall from Senegal to Djibouti was long touted as the solution for halting desertification in the Sahel, the arid savanna on the south border of Africa’s Sahara desert. But its implementation has been lacking in nine of the 11 countries in the region, a study by McGill University found. The researchers proposed a shift from planting trees to utilising shrubs which had a faster growth rate and longevity.When they survive at all, saplings take years to grow into trees. Given the propensity of our authorities to peddle suicidal policies, Delhi as we know it may not even exist that long. Forget 16,000, the capital cannot afford to lose a single tree to construction. And it is for us, the residents, to ensure that it doesn’t.