What you might have missed: mass extinction, infrared mirrors, birds cooperate with humans, and concrete waste.

Humans and birds work together to find a sweet treat

In many parts of Africa, humans communicate with a species of wax-eating bird called the greater honeyguide, Indicator indicator. These helpful birds lead people to wild bees’ nests to increase their own chances of snacking on calorie-dense honey and beeswax.

The human honey-hunters communicate with wild honeyguides using calls, and a new study in Science has found that honeyguides are more likely to cooperate with people using the local, familiar sounds.

Hadza honey-hunters in Tanzania communicate with honeyguides using a melodic whistle, whereas Yao honey-hunters in Mozambique use a trill followed by a grunt.

“We found that honeyguides prefer the calls given by their local human partners, compared to foreign calls and arbitrary human sounds,” explains Dr Claire Spottiswoode, an evolutionary biologist at the University of Cambridge and the University of Cape Town.

“This benefits both species, since it helps honey-hunters attract a honeyguide to show them hard-to-find bees’ nests, and helps honeyguides to choose a good partner to help them to get at the wax.”

Transforming concrete waste with graphene

Global demolition and construction waste products are expected to rise to almost 2.6 billion tonnes by 2030. The production of new concrete releases greenhouse gas emissions that contribute to climate change.

Australian researchers are developing a new way to improve concrete sustainability by upcycling old broken concrete to strong, durable, and workable concrete. The method involves soaking the recycled coarse aggregates in small amount of graphene solution.

“This new form of treated recycled concrete aggregates may be more expensive to make right now, but when considering circularity and the life cycle of the materials, the costs are coming down rapidly,” says Dr Aliakbar Gholampour of Flinders University, the first author in a new article in Resources, Conservation and Recycling.

Understanding the end-Triassic mass extinction

About 200 million years ago, Earth experienced its 4th major mass extinction event – ending the Triassic period and launching the Jurassic. It was triggered by a dramatic rise in greenhouse gases due to volcanic activity, which led to rapid global warming.

“We wanted to understand not just what survived and what didn’t, but the roles that different species played as the ecosystem changed. This approach helps us see the broader, interconnected ecological picture,” says Professor David Bottjer of the University of Southern California Dornsife, senior author of a new study in Proceedings of the Royal Society B.

The new research found that the impact of the extinction event was different between marine and terrestrial ecosystems. Nearly 71% of the ocean’s genera (categories of species) vanished, but the overall structure of marine ecosystems showed resilience. Conversely, 96% of terrestrial genera went extinct, dramatically reshaping of life on land.

“We’re seeing similar patterns now — rapid climate change, loss of biodiversity. Learning how ecosystems responded in the past can inform our conservation efforts today,” adds Bottjer.

The perfect high-performance mirror

In the field of high-performance mirrors, the ultimate goal is to create coatings with perfect reflectivity. In the visible range of wavelengths – between 380 nanometres and 700 nm – the most advanced mirrors can be as high as 99% reflective. This means that 1 photon is lost for every 99 reflected.

This might seem impressive, but near-infrared mirrors – between ~780 nm and 2.5 micrometres – can be up to 99.9997% reflective, losing only 3 photons out of 1 million. 

Mid-infrared mirrors lose roughly 1 out of every 10,000 photons, about 33 times worse.

Now, a team of researchers has demonstrated the first true mid-infrared supermirrors in a new study in Nature Communications. These mirrors reflect wavelengths between 2.5 µm to 10 µm and lose only 8 photons out of 1 million, achieving a reflectivity of 99.99923%.

One application of the new supermirrors will be to improve the sensitivity of optical devices, called cavity ringdown spectrometers, that are used to detect and quantify trace amounts of gases.