IELTS Reading practice

For most of the twentieth century, city planners treated trees as decoration — a pleasant but optional finish applied once the important work of roads and buildings was done. That view has changed sharply. A growing body of research now treats the urban tree canopy as a piece of public infrastructure, as measurable in its effects as a drainage pipe or a bus route, and arguably cheaper to maintain.

The clearest benefit is temperature. Dense city materials such as asphalt and concrete absorb heat during the day and release it slowly at night, producing the so-called urban heat island. A mature tree counters this in two ways: its canopy shades surfaces that would otherwise bake, and the water it releases through its leaves cools the surrounding air, much as sweat cools skin. Streets lined with large trees can be several degrees cooler than bare streets only a short distance away.

The effects reach beyond comfort. During heatwaves, shaded neighbourhoods record fewer hospital admissions for heat-related illness, and lower nighttime temperatures help residents sleep, which has its own knock-on effects on health and productivity. Trees also intercept rainfall, slowing the rush of water into drains during storms and reducing the flooding that increasingly troubles dense cities.

Yet the benefits are not shared evenly. Surveys across many cities have found that wealthier districts tend to have markedly more canopy cover than poorer ones. Because the cooling and flood-control effects are real, this gap means that the residents least able to afford air conditioning or to recover from a flooded home are often those with the least natural protection. Some city governments have responded by setting canopy targets for under-planted districts, though trees planted today take decades to deliver their full value.

Planting is also harder than it looks. A sapling pushed into a narrow pit beside a road, its roots hemmed in by pipes and compacted soil, may struggle for years and die young. Specialists now argue that the soil volume available to a tree matters more than the number of trees planted, and that a smaller number of well-rooted trees will outperform a larger number of neglected ones. The unglamorous work, in other words, happens below the pavement.