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A new study is challenging one of the most comforting assumptions in urban climate design: that adding vegetation to dense cities always makes hot weather safer. Research published in npj Urban Sustainability reports that compact, high-rise urban forms can amplify humid heat risks associated with vegetation transpiration—a process usually considered an essential cooling service. The finding does not suggest that trees and plants should be removed from cities. Instead, it reveals that the success of green infrastructure depends heavily on building geometry, airflow, humidity, and the way heat and moisture move through the urban atmosphere.

Vegetation transpiration occurs when plants release water vapor through microscopic openings in their leaves. This process consumes energy and can lower leaf and surrounding air temperatures, much like evaporation from human skin. In a well-ventilated environment, the added moisture may be dispersed efficiently, allowing evaporative cooling to provide a net thermal benefit. But in tightly packed high-rise districts, the same moisture can become trapped between buildings. The result is a more humid microclimate in which the body’s ability to cool itself through sweating is weakened.

That distinction matters because humid heat is more dangerous than air temperature alone suggests. The human body relies on evaporation to transfer heat away from the skin. When atmospheric moisture is already high, sweat evaporates more slowly, forcing the body to work harder to maintain a stable internal temperature. Heat-stress indicators such as wet-bulb temperature and the Wet-Bulb Globe Temperature account for this interaction between heat and humidity. A neighborhood with slightly lower temperatures but substantially higher humidity can therefore feel more oppressive—and pose greater health risks—than a drier location with hotter air.

The study focuses on the urban “canyon” effect created by tall buildings arranged close together. These structures can obstruct wind, reduce the exchange of air with the atmosphere above, and alter the amount of sunlight reaching streets and façades. When vegetation in such spaces transpires, the released water vapor may accumulate rather than disperse. The compact geometry can also create complex circulation patterns, with warm and moist air repeatedly moving through pedestrian-level spaces. In this setting, greenery may cool surfaces while simultaneously increasing the moisture burden experienced by people outdoors.

This is a crucial refinement of the popular idea that urban greening is universally beneficial. Plants perform several valuable functions: they provide shade, intercept solar radiation, reduce surface temperatures, store carbon, and improve the visual and psychological quality of public space. Yet their cooling performance is not fixed. It changes with species, soil moisture, canopy density, irrigation, wind conditions, building height, street width, and background humidity. The new research emphasizes that these factors must be evaluated together rather than treating vegetation as an isolated solution to urban heat.

The implications are particularly significant for rapidly growing cities where vertical development is being used to accommodate rising populations. High-rise construction can reduce land consumption, but dense towers may produce localized atmospheric conditions that differ dramatically from those in surrounding neighborhoods. A cooling strategy designed for an open suburban street may behave differently in a narrow urban canyon surrounded by tall façades. Planners could therefore face a difficult balancing act: maximizing shade and ecological benefits without creating stagnant pockets where moisture and heat combine into dangerous conditions.

The findings also raise questions about how cities measure the success of climate adaptation projects. A street may record a lower surface temperature after trees are planted, yet still expose pedestrians to greater physiological stress if humidity increases and air movement declines. This means future assessments should include multiple variables, including air temperature, relative humidity, wind speed, radiant heat, and human thermal response. Satellite observations and conventional weather stations may not fully capture conditions at street level, where building walls, tree canopies, pavement, and human activity interact within a few meters.

The research is likely to intensify debate over “smart” urban greening rather than green infrastructure in general. Possible responses include selecting vegetation according to local humidity and wind conditions, designing wider or better-connected ventilation corridors, combining trees with reflective or permeable surfaces, and ensuring that shaded areas do not become poorly ventilated enclosures. Building orientation and spacing may be as important as the number of trees planted. Irrigation practices could also matter, since additional water supplied to vegetation may increase transpiration during precisely the periods when atmospheric moisture is already high.

For residents, the message is both cautionary and practical. A leafy street can still be healthier than an exposed one, particularly when shade reduces direct solar radiation. But during extreme heat, people should not assume that every green space offers the same level of protection. Dense, humid, windless areas may require additional measures such as cooling centers, drinking-water access, timed outdoor activities, and heat alerts that account for humidity. The study’s central contribution is to show that urban climate risk is not determined by temperature alone—or by the presence of greenery alone—but by the interaction between city form, plant physiology, and human vulnerability.

As climate change increases the frequency and intensity of heat extremes, these interactions could become more consequential. The research presents cities with a deceptively simple lesson: cooling the urban environment is not just a matter of adding more plants. It requires understanding where the water released by vegetation goes, how buildings control its movement, and how the resulting air feels to a human body. In the race to make cities greener, the next generation of design may need to be equally focused on keeping them breathable.

Subject of Research: The relationship between compact high-rise urban form, vegetation transpiration, humidity, and humid heat risk.

Article Title: Urban high-rise compact form amplifies humid heat risk from vegetation transpiration.

Article References: Zhang, Y., Yang, K., Zhu, Y. et al. “Urban high-rise compact form amplifies humid heat risk from vegetation transpiration.” npj Urban Sustainability (2026). https://doi.org/10.1038/s42949-026-00459-1

Image Credits: AI Generated

DOI: 10.1038/s42949-026-00459-1

I continue to have problems with Contacts in Tahoe. The latest issue is that the Messages app constantly displays a banner showing that one of my contacts has updated her poster. I don’t want to use it; I want to keep the photo that I chose. But clicking the × button does not dismiss the New poster available from [Person] banner. It remains anchored atop that conversation.

Sidenote: I hate that it wants me to click Update Contact but that the image shown is the old photo. How can I commit to the new photo without even knowing what it looks like? How can I undo if I don’t like it?

Sidenote 2: I’m also getting repeated Siri found an event banners in Messages, but they go away after about three clicks. They’re extra annoying because (unlike above) they animate in again each time I dismiss them, and they’re for events that are already on my calendar.

I thought maybe I could fix things by going into the Contacts app. Unfortunately, the Contact Photo & Poster button there is inoperative. Sometimes it flickers when I click it. Sometimes nothing happens at all. Sometimes after clicking the button it will open the photo chooser sheet for the next contact that I view.

I just want a single setting to let me choose my own photos. I never want to use a poster or be notified that one has changed.

Ben Lovejoy:

Ternus, said he was committed to building on the company’s momentum in the entertainment business when he takes the helm of the iPhone maker in September […]

“I think we have such tremendous momentum right now in ​Apple TV,” Ternus told Reuters on the red carpet at the premiere of the fourth season of Ted ​Lasso. “There’s so many amazing shows, so many amazing characters and stories, and so we’re just going to keep building on the momentum.”

Have we seen any indication yet that he cares about software?

Previously:

• Apple Financial Statements: Products vs. Services
• Contacts in Tahoe
• Turning Off iOS 17 Contact Posters

Breathing clean air depends on filters that do more than trap particles—they must hold them. In many conventional systems, captured dust can loosen under airflow and mechanical disturbances, which lowers filtration efficiency, shortens service life, and forces more frequent replacement. The bottleneck is not capture alone, but durable retention of what the filter catches.

A research team led by Professor Sanghyuk Wooh and Professor Chae Bin Kim has introduced a dynamic imine bond adhesive (DIBA) designed to keep airborne particles embedded. The concept is to marry solid-like stability with liquid-like adhesion, so the filter surface can “refresh” itself while working.

The coating is built by crosslinking polydimethylsiloxane (PDMS) via dynamic Schiff base chemistry. This chemistry enables bond exchange at the interface, allowing adhesive sites to reorganize over time rather than degrade into inert residue. The result is a coating that is both mechanically robust and chemically active.

When sprayed onto commercially available filter media, the DIBA layer behaves like an internal reservoir of stickiness. As particles are collected, they are drawn into the adhesive film rather than remaining only on the exterior fibers. Capillary-driven wetting then forms adhesive bridges around individual particulates, increasing the real contact area that governs holding strength.

Performance tests combined chemical, mechanical, and interfacial characterization—rheology, FTIR, atomic force microscopy, and microscopy—with filtration trials. The coating boosted particle adhesion dramatically, approaching a nearly seventy-fold improvement compared with typical behavior. Importantly, the adhesive renewal process helps counteract the gradual loss of attachment that plagues standard filters.

Filtration efficiency improved by roughly 10–30% across multiple commercial materials, without raising pressure drop. The upgrade is significant in practical terms: one reported shift is from MERV 6 toward MERV 11, indicating better capture at the same airflow penalty.

The coated filters also sustained operation under high-speed airflow (up to 20 m/s) and delayed pore clogging. By maintaining effective particulate capture for longer intervals, the DIBA approach extended filter lifespan by nearly a factor of two relative to conventional designs.

Because DIBA is applied through simple spray-coating, it is compatible with existing manufacturing and retrofit workflows. The researchers highlight applications ranging from HVAC and air purifiers to cleanrooms, industrial dust collectors, automotive cabin filters, and personal protective equipment.

More broadly, the work suggests a platform for next-generation filtration where energy use and replacement schedules improve simultaneously. The dynamic adhesive strategy could be adapted to other separations, including water purification and environmental remediation, wherever particles need to be captured and kept immobilized.

Subject of Research: Not applicable
Article Title: A Super-Adhesive Air Filter With Capillarity-Mediated Spontaneous Particle Absorption via Dynamic Bond Exchange
News Publication Date: 22-Apr-2026
Web References: https://doi.org/10.1002/adma.202600006
References: DOI: 10.1002/adma.202600006
Image Credits: Professor Sanghyuk Wooh from Chung-Ang University, Republic of Korea and Professor Chae Bin Kim from Pusan National University, Republic of Korea

Keywords

Air filtration, dynamic adhesive chemistry, Schiff base, PDMS, particle retention, capillarity, MERV, particulate matter, surface engineering, polymers

On July 24, 2006, the world got its first glimpse of Apple's new wireless Mighty Mouse due to an FCC filing. It became an instant winner.

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