A new study led by the University of Cambridge offers fresh insights into how urban tree canopies, while effective at cooling cities during the day, may inadvertently trap heat at night.

As global temperatures continue to rise, many cities are grappling with the effects of urban heat stress, which is linked to increased illness, energy consumption, and social inequality. Excessive heat can also damage urban infrastructure, highlighting the urgent need for effective mitigation strategies. Among these, tree planting has become a central component of efforts to cool down cities.

However, a recent study led by the University of Cambridge warns that not all tree species or planting methods are equally effective in reducing urban temperatures. According to Dr. Ronita Bardhan, Associate Professor of Sustainable Built Environment at the University of Cambridge’s Department of Architecture, “Trees have a crucial role to play in cooling cities down but we need to plant them much more strategically to maximize the benefits they can provide.”

New Insights on Tree Cooling and Heating Effects

Published in Communications Earth & Environment, the study offers the first comprehensive global assessment of urban tree cooling. By analyzing 182 studies from 110 cities worldwide, the research reveals how tree planting can lower pedestrian-level air temperatures by up to 12°C, with 83% of cities studied achieving temperatures below the “thermal comfort threshold” of 26°C. However, the study also shows that the cooling effects of trees can vary dramatically depending on species, climate, and urban design.

Dr. Bardhan noted, “Our study busts the myth that trees are the ultimate panacea for overheating cities across the globe. The cooling effects of trees are complex and vary significantly depending on the context in which they are planted.”

Cooling Benefits Vary by Climate Type

The study found that urban trees tend to be more effective in cooling cities in hot, dry climates compared to those in humid, tropical areas. In hot and dry climates like Nigeria’s savanna, trees can lower city temperatures by as much as 12°C during the day, but can also increase nighttime temperatures by up to 0.8°C. In arid climates, trees were shown to cool cities by just over 9°C but also raise nighttime temperatures by 0.4°C. Conversely, in tropical rainforest climates, daytime cooling was limited to about 2°C, with nighttime warming reaching 0.8°C.

“Trees perform best in dry, hot climates, but in tropical regions with high humidity, their nighttime warming effect can negate their daytime cooling benefits,” said Dr. Bardhan.

Strategic Tree Planting: The Key to Maximizing Cooling

The study underscores the importance of planting trees in a way that aligns with a city’s specific urban form and climate conditions. Cities with open layouts, for instance, benefit from a mix of evergreen and deciduous trees of varying sizes, leading to more effective cooling across different seasons. In contrast, compact urban layouts, like those in Cairo or Dubai, favor evergreen species that are better suited to dry, hot conditions.

The researchers found that mixed-species planting could provide up to 0.5°C more cooling than monoculture tree planting, as different trees offer varying levels of shade and sunlight penetration at different heights. Furthermore, larger green spaces allow for bigger tree canopies, leading to better overall cooling in dry climates.

“Our study provides context-specific greening guidelines for urban planners to more effectively harness tree cooling in the face of global warming,” Dr. Bardhan said. “Urban planners need to plant the right mix of trees in optimal positions to maximize cooling benefits.”

Looking to the Future: Planning for Warmer Climates

The study also stresses that as climate change progresses, it is essential for cities to choose resilient tree species that will continue to thrive under hotter conditions. “Urban planners should plan for future warmer climates by choosing resilient species which will continue to thrive and maintain cooling benefits,” Dr. Bardhan emphasized.

Furthermore, the researchers note that trees alone cannot solve the issue of urban heat. To complement tree planting, solutions like solar shading and reflective materials should continue to play a vital role in mitigating the heat effects in cities.

A Tool for Urban Planners

In an effort to make these findings more accessible, the researchers have developed an interactive database and map that allows users to estimate the cooling efficacy of different tree planting strategies based on the climate and urban characteristics of cities worldwide. This tool will help urban planners design more effective, climate-specific tree planting schemes.

A new study has identified a gene mutation that could be a key factor in the development of autism spectrum disorder (ASD) in early childhood. The research, led by Dr. Jackson James and his team, at by the Rajiv Gandhi Centre for Biotechnology (RGCB), Kerala, India, highlights how a mutation in the Tlx3 gene may disrupt cerebellum development, leading to autism-related behaviours. The findings were published in the journal iScience.

Autism, a developmental disorder affecting brain function, is known to result from a combination of genetic and environmental factors. Symptoms of ASD can appear as early as the age of two, and the disorder often involves complex genetic mutations, including those affecting early developmental genes.

In their study, the RGCB team focused on the Tlx3 gene, which plays a crucial role in the development of the cerebellum — a brain region responsible for balance, motor skills, and coordination. By deleting the Tlx3 gene in the cerebellum of genetically modified mice embryos, the researchers observed significant disruptions in motor function, which later manifested as hallmark symptoms of autism in adulthood. These included impairments in social skills, repetitive behaviours, and motor movement issues.

Symptoms of ASD can appear as early as the age of two, and the disorder often involves complex genetic mutations, including those affecting early developmental genes

The study also explored the mutation’s potential presence in the human population. In collaboration with the CSIR-IGIB (Institute of Genomics and Integrative Biology) in New Delhi, the team found variants of the TLX3 mutation linked to nine cases of ASD and other neurodevelopmental conditions.

Dr. James emphasized the need for further research, stating, “A genome-wide global cohort analysis is necessary to assess the frequency of this TLX3 mutation and its prevalence in specific populations, such as Indians and others.” The study underscores how improper regulation of early embryonic genes can contribute to the onset of ASDs during early childhood.

Prof. Chandrabhas Narayana, Director of RGCB, said, “Autism is a serious childhood problem across the world. In India, it has emerged as a significant challenge for researchers and the medical community due to its broad social and medical impacts. The RGCB study will offer new insights into this behavioural disorder.”

ASDs are characterized by a range of behavioural deficits, including challenges with social cognition, communication, and repetitive behaviours, which affect individuals’ ability to engage with their environment and peers.

When we think of slow and steady, the image of a tortoise often comes to mind. But behind that unhurried gait lies a remarkable creature capable of defying time itself. The tortoise is among the longest-living animals on the planet. Their extraordinary lifespan has fascinated biologists and storytellers alike, leading us to wonder: how do these creatures live so long? Is it the giant tortoises of the Galápagos or the smaller, land-dwelling species that hold the key to longevity? Let’s take a deeper look.

A Life of Patience and Persistence

The tortoise’s slow walk is not just a quirky trait — it’s a life philosophy, ingrained in their very survival. These creatures are not in a race against time, they are its patient conquerors. Some species of tortoises can live well over a century, and in the case of the Giant Tortoise (known for its immense size), individuals have been documented living for more than 200 years. But why is it that these ancient reptiles live so long, while their cousins, the turtles, tend to have shorter lifespans?

In terms of lifespan, tortoises—especially the giant tortoises—lead the pack. A giant tortoise can outlive many other creatures, including their ocean-dwelling cousins, the turtles. While turtles generally live between 50 to 100 years, giant tortoises surpass this, sometimes even living beyond 150 years. In fact, Jonathan, a Seychelles giant tortoise living on Saint Helena Island in the South Atlantic, holds the record as the world’s oldest living land animal at 189 years old. Jonathan, who was born in 1832, has outlived all of his peers, continuing to thrive on the island where he was discovered.

The Science Behind Their Longevity

The secret to the tortoise’s longevity lies deep within its biology. While there are several factors that contribute to their long lives, two of the most significant are evolutionary adaptations and cellular processes that are finely tuned to conserve energy and maintain health over decades.

From an evolutionary perspective, tortoises face fewer natural threats in their environment compared to faster, more vulnerable animals. For many species of tortoises, survival has been less about outpacing predators and more about outlasting them. Many tortoises lay multiple eggs, often many more than a single clutch, and they continue to reproduce over several decades. This “quality over quantity” approach to reproduction ensures that their genes continue to thrive, while their individual lifespans stretch out.

Moreover, tortoises tend to have slower metabolic rates compared to other animals. Their bodies conserve energy by keeping their metabolic processes at a steady, slow pace. This “slow burn” strategy is key to their extended lifespans. A slow metabolism means that fewer cellular processes are damaged by the wear and tear of daily life, which translates into fewer health issues in old age.

One of the most fascinating aspects of tortoise longevity is the role of their telomeres. Telomeres are the protective caps at the ends of chromosomes that prevent them from fraying and tangling. Every time a cell divides, the telomeres shorten slightly. In most organisms, as the telomeres shorten, cells lose their ability to divide, eventually leading to aging. However, in tortoises, the telomeres wear down at an unusually slow rate, allowing their cells to divide without the usual detrimental effects seen in other animals. This slower rate of telomere shortening helps them avoid age-related diseases such as cancer and ensures that their cells remain healthier for longer.

Furthermore, some studies have revealed that tortoises are capable of a process called apoptosis—a form of programmed cell death—where damaged or dysfunctional cells are destroyed before they can cause harm. This controlled form of self-destruction in damaged cells helps prevent the formation of tumors and other age-related diseases, which is another reason for the tortoise’s impressive lifespan.

The Giants of the Tortoise World

When we talk about longevity in tortoises, we cannot overlook the giant tortoises of the Galápagos Islands and the Seychelles. These remarkable creatures have not only captured our imagination but have also become living symbols of resilience and endurance.

The Galápagos Giant Tortoise, for instance, can live over 150 years, and some individuals have even outlived the scientists who studied them. They were once thought to be heading for extinction, but thanks to conservation efforts, their populations have stabilized.

In India, a rare breed of tortoise known as the Aldabra Giant Tortoise has been known to live up to 255 years. This species, although not as well-known as the Galápagos counterparts, is another testament to the wonders of nature’s design.

Turtles, which are often found in aquatic environments, tend to live shorter lives, averaging about 30 to 50 years

But what about other, lesser-known giants? In Kasaragod, Kerala, India, a giant soft-shell turtle species was discovered in May 2021, which lives in freshwater, weighing over 100 kilograms! These giant creatures are living proof of the astonishing adaptability and longevity that nature has to offer.

The Mystery of Tortoises and Turtles

While all tortoises are technically land-dwelling creatures, there is an interesting distinction between tortoises and turtles. Turtles, which are often found in aquatic environments, tend to live shorter lives, averaging about 30 to 50 years. Tortoises, on the other hand, tend to have larger bodies, longer necks, and more robust shells. Their heavy, often plant-based diet plays a role in the additional years they add to their lifespan.

A surprising discovery made in the Seychelles in recent years has sent shockwaves through the scientific community: certain tortoises, once thought to be herbivorous, have been seen eating birds and other small animals. This has raised questions about the adaptability of tortoises in changing environments and has piqued the interest of researchers studying their survival strategies.

What Lies Ahead?

Despite all that we know about these extraordinary creatures, there is still much to discover. Researchers continue to study tortoises, particularly the giant species, to learn how their unique biological traits could benefit human medicine, particularly in the fight against aging and diseases like cancer. The discovery of their telomere dynamics, coupled with the ability to prevent cell damage through apoptosis, could one day revolutionize the way we approach longevity and healthcare.

For now, we can only marvel at the tortoise’s timeless existence, its slow, steady journey through the ages, and the lessons it teaches us about patience, resilience, and the secrets of life’s most enduring creatures.