For many years, the strategy to combat overheating in concrete megacities has been to increase the number of green spaces. However, a new scientific study suggests that in regions with high humidity, this natural method may cause discomfort for residents.
Researchers from the Indian Institute of Technology (IIT) Gandhinagar and the University of Northeastern in the USA found that in humid urban environments, dense tree canopies can become a source of increased humidity and heat. They impede air circulation, leading to a rise in perceived temperature to dangerous levels.
The team analyzed data collected in 138 Indian cities between 2003 and 2020. Studying diverse climatic zones—from the arid northwest to the tropical south—the scientists sought to understand why urban greening benefits some places but proves ineffective in others.
It was established that the effectiveness of urban greening directly depends on the local climate and landscape characteristics. Vegetation typically cools the area in two main ways: shading and evapotranspiration.
Shading is a simple mechanism: leaves block solar radiation, preventing it from reaching buildings and ground, thereby reducing energy input. Evapotranspiration is more complex; it is the process by which plants release water vapor, consuming heat and lowering the surrounding air temperature.
In dry, arid cities, this process is very beneficial because the air can effectively absorb moisture, providing significant cooling. However, in cities with high humidity, the air is already saturated with water. When dense clusters of trees additionally release moisture through evapotranspiration, the atmosphere becomes heavy and stuffy.
The situation is exacerbated if the city's architecture, such as tall buildings and narrow streets, obstructs wind. As a result, moisture gets trapped. For humans, this creates extremely unfavorable conditions. The human body cools down through sweat evaporation from the skin. If the air is already saturated with moisture from local trees, sweat cannot evaporate, and a person feels a significantly higher temperature than what the thermometer indicates.
This perceived heat is known as the Heat Index, and this indicator was used by researchers to measure thermal discomfort.
The researchers applied machine learning methods and high-resolution satellite imagery to determine specific thresholds beyond which greening ceases to be beneficial. They found that moderate leaf area and overall greenery usually contribute to cooling, but when plant health or productivity (measured as fPAR) exceeds a certain limit in humid urban centers, the Heat Index begins to rise.
In some cases, dense greening in humid Indian cities was linked to an increase in the feeling of heat by two degrees Celsius. This indicates the need for a serious revision of standard policies that always favor more greenery in tropical climates.
Previously, studies often relied on land surface temperature measurements, which show how hot the asphalt appears from space. Nevertheless, surface temperature does not reflect the actual human experience. This new study focused on the Heat Index, which combines air temperature and humidity for a more accurate assessment of the impact of urban heat on public health.
Furthermore, the analysis of 138 cities over nearly two decades provided a large-scale view of these trends, unlike small computer simulations that may not account for the complex reality of urban life.
As climate change makes heatwaves more frequent and intense, there is a strong drive to plant forests on every available patch of land. However, this study demonstrates that a climate-adapted approach to design is critically important. In humid cities, planners should consider prioritizing the creation of sparse canopies that ensure better ventilation or focusing on strategic building shading, rather than relying solely on dense clusters of highly transpiring trees.
By identifying where and why nature-based solutions might be counterproductive, this allows governments to develop fairer and more effective cooling strategies. For millions of people living in rapidly warming tropical cities, these findings could be the deciding factor between a city sanctuary and a suffocating trap of humid heat.
Avocados are rich in nutrients, but buying the fruit can be expensive. Farmer Harmanpreet Singh claims that one can grow their own tree at home from just one seed with patience.
For over ten years, Harmanpreet helped establish avocado cultivation enterprises in countries such as Ethiopia, Rwanda, and Kenya. After returning to Amritsar, he wanted more Indians to enjoy this fruit, which they had not previously considered for cultivation.
He notes that an avocado tree can bear fruit for almost 50 years, which convinced him of the value of presenting this plant to people, as it requires little effort but yields fruit for decades.
The process begins with planting a seed taken from a ripe avocado. It should be planted in a mixture of soil, coconut fiber, and compost, ensuring the top part of the seed remains above the soil surface to prevent rot.
The container needs to be placed in a warm spot where the temperature stays above 25 degrees Celsius. Watering should be moderate, and vermicompost should be added over the next twenty days while the seed slowly prepares to sprout.
When the stem reaches about 15 centimeters, it must be transplanted into a larger pot. A sunny terrace will suffice for further growth into a healthy avocado plant.
It is important to avoid excess water; the soil should remain moist but not waterlogged. If the leaves start to yellow, it is a sign that the plant has received too much water.
After 60–90 days in a large pot, when the stem is the thickness of a pencil, it should be grafted onto a healthy mother plant to stimulate better growth and increase yield.
Harmanpreet points out that avocados naturally contain Persin—a fungicidal toxin that helps repel many pests and birds, thus reducing dependence on chemical fertilizers.
According to Harmanpreet, if the plant is grown independently, it will yield two kilograms of fruit in the first two years, and by the tenth year, it can produce up to 1.5 quintals annually. Thus, one seed can provide benefits for decades.
An incident at the Monte Real pumping station, located in the municipality of Leiria, on August 12, 2025, resulted in the discharge of thousands of cubic meters of untreated effluent into the Lis river. This river flows into Praia da Vieira, in the municipality of Marinha Grande, and also into irrigation ditches.
The Portuguese Environment Agency calculated that between 20,000 and 25,000 m3 of raw sewage were discharged into the river. As a consequence, swimming at Praia da Vieira was suspended for three days, and the Municipality of Leiria advised against activities such as fishing, swimming, and water abstraction for irrigation in the stretch of the Lis river below Monte Real.
The City Council of Marinha Grande established a support service for those affected by the discharges, assisting in preparing compensation claims with AdCL. The responsible company informed Lusa that it registered 12 manifestations from potential victims, communicated to AdCL after a survey conducted through a form made available by the Municipality of Marinha Grande.
These manifestations include both individuals and entities linked to various economic activities, being most frequent in the agricultural, fishing, catering, and commerce sectors. The total amount requested by the claimants approaches 256 thousand euros, with individual amounts varying between 400 and 160 thousand euros.
AdCL clarified that immediately after the accident, it activated the relevant insurance policies and transferred the management and analysis of possible claims to its insurer, stating that no compensation had been paid to date. The process is still under evaluation by both the insurer and the appointed expert.
The company explained that it awaits the insurer's final decision on how to classify the claim within the current policies and, consequently, regarding the submitted claims, without being able to provide a forecast for the process completion by the insurer at this time.
After the incident, AdCL requested a Technical Study for Environmental Damage Assessment and Mitigation Measures. The company guaranteed that it is implementing actions to strengthen the safety, resilience, and response capacity of the sanitation system connected to the Lis river.
Among the improvements already made or underway, the reinforcement of the ultraviolet disinfection system at the Coimbra WWTP, completed at the beginning of the year, stands out, aiming to increase treatment efficiency and environmental safety. Furthermore, the repair and reinforcement of the pumping system at the Monte Real pumping station, the site of the accident, have been completed, with the goal of reducing the risk of similar future events.
Currently, the project to direct the effluent from the Vieira de Leiria WWTP for treatment at the Coimbra WWTP is in the proposal submission phase.
Additionally, the impact of the 'storm train' at the beginning of the year added to the problem of the summer of 2025, causing damage to several AdCL infrastructures and requiring a continuous operational response to restore normal system functioning conditions.
The first recorded specimen of the northern bat has been discovered on the Iberian Peninsula. This species is the only one that breeds north of the Arctic Circle, and previously its populations were mainly found in Scandinavia, Finland, Russia, and the Alps.
In a single night, the scientific expedition managed to capture a total of 231 bats from 12 different species, including the northern bat (Cnephaeus nilssonii).
This is the first documented evidence of the presence of the northern bat on the Iberian Peninsula. This species is considered one of the most northern on the planet, previously restricted to the northern regions of Europe and the Alps.
The northern bat is unique in that it is the only known bat species that breeds north of the Arctic Circle. This is due to its ability to adapt to harsh winters and cold conditions.
This adaptation is achieved through an outstanding ability to enter a state of torpor—a kind of false hibernation lasting less than 24 hours—and reduce metabolism to conserve energy.
Scientists are currently trying to determine whether this population represents a previously unknown group established in the Cadí-Moixeró Natural Park; whether it is a species that migrated from the Alps; or if other populations survived the last ice age and have not yet been found in southern Europe.
A possible connection with the presence of the European silver bat (Vespertilio murinos), which also has a northern distribution and was recently identified by the same team in the Cadí-Moixeró Natural Park, is also being investigated.
The team of scientists is completing the morphological and genetic study of the bat and preparing a scientific publication that will describe this first observation on the Iberian Peninsula.
The company plans an investment of approximately one million euros to increase the resilience of four pumping stations, aiming to raise operational reliability, reduce vulnerability in critical situations, and ensure greater emergency response capacity.
In its investment plan, AdCL also foresees the remodeling of the Coimbra WWTP, with an estimated cost of 32 million euros, to adapt this infrastructure to the new requirements of the Urban Wastewater Directive. According to Águas do Centro Litoral, this investment will help significantly improve the quality of the effluent discharged into the Lis river.
