Yours

Li Hua

3 . The forest of today will not be the forests of tomorrow. Rising temperatures, trees being cut down, development and climate-change-caused disasters are changing the very makeup of the Earth’s forests, new research published in Science finds.

Older, bigger trees are being lost at an alarming rate, making the planet’s forests shorter and younger. The change is being driven at different rates by different causes in different places, the study’s authors say, but the consequences will be global.

Old growth forests absorb and store massive amounts of climate-warming CO₂. They provide habitats for rare and endangered species and promote rich biodiversity. Researchers found that the world lost roughly one-third of its old growth forests between 1900 and 2015. In North America and Europe, they found that tree mortality has doubled in the past 40 years.

“Warming temperatures, wildfires, logging and insect outbreaks were among the many causes of the decline,” says Nate McDowell, the study’s lead author. “What’s perhaps more concerning is that the trajectory of all these disturbances is generally increasing over time and is expected to continue increasing in the future.” he says.

McDowell’s focus is on how trees are affected by rising temperatures, arguably the biggest driver of forest change. To get a broader understanding of how forests are changing globally, he brought in more than 20 other researchers in different fields. Together, they examined more than 160 previous studies about tree mortality and its global causes, applying current satellite data and modeling to create a look at the Earth’s changing forests to date.

“It’s not a shock, but it’s very sad,” says Kristina, an ecologist and leader of the ForestGEO Ecosystems &Climate Program who helped with the research. “We as a human society are hitting these forests so rapidly with so many different changes that they can’t keep up.” she says.

4 . Wildlife populations around the world are facing dramatic declines, according to new figures that have led environmental campaigners to call for urgent action to rescue the natural world. The 2022 Living Planet Index (LPI), produced by the Zoological Society of London (ZSL), reveals that studied populations of mammals, birds, reptiles (爬行动物) and fish have seen an average decline of 69 per cent since 1970, faster than previous predictions. The LPI tracked global biodiversity between 1970 and 2018, based on the monitoring of 31,821 populations of 5230 vertebrate (脊椎动物) species. Mark Wright of WWF says the degree of decline is destructive and continues to worsen. “We are not seeing any really positive signs that we are beginning to bend the curve of nature,” he says.

Freshwater vertebrates have been among the hardest-hit populations, with monitored populations showing an average decline of 83 per cent since 1970. The Amazon pink river dolphin, for example, has experienced a 65 per cent decline in its population between 1994 and 2016. Meanwhile, some of the most biodiverse regions of the world are seeing the steepest falls in wildlife, with the Caribbean and central and south America seeing average wildlife population declined by 94 per cent since 1970. Habitat loss and reduction is the largest driver of wildlife loss in all regions around the world, followed by species overexploitation by hunting, fishing or poaching (偷猎).

In December, governments from around the world will gather in Montreal, Canada, for the COP15 Biodiversity Framework, a much-delayed summit that aims to agree on a set of new targets intended to prevent the loss of animals, plants and habitats globally by 2030. “This is a once-in-a-decade opportunity that’s coming up,” says Robin Freeman of ZSL. He says it is vital that governments use the summit to agree on “meaningful, well measurable targets and goals”. “We need governments to take action to ensure that those goals deal with the complicated combined threats of climate change and biodiversity, in order for us to see a meaningful action,” says Freeman. But some researchers are critical of the LPI’s use of a headline figure of decline, warning it is easy to be misunderstood.

The findings don’t mean all species or populations worldwide are in decline. In fact, approximately half the populations show a stable or increasing trend, and half show a declining trend. “I think a more appropriate and useful way to look at it is to focus on specific species or populations,” says Hannah Ritchie at Our World in Data. But Wright says the LPI is a useful tool that reflects the findings of other biodiversity indicators. “All of those show they all scream there is something going really very badly wrong,” says Wright.

8 . We’re shopping online more than ever now, including various personal care and food items. Of U.S. Internet users, one-third do it at least once a week. Seeing your limited toilet paper (TP), you might pull up your smartphone and after a few taps have a fresh order of TP set to arrive in a day, maybe even less, and all done right from the toilet seat.

But this type of shopping — numerous small, quick-to-ship orders placed through e-tailing companies like Amazon — might be the worst for the environment, according to a recent study in Environmental Science & Technology. With their current business model of free shipping and fast delivery, greenhouse gas emissions linked with transporting “fast consumer goods” are high. “The online-only retailers are growing rapidly,” says lead author Sadegh, a scientist at Radboud University in the Netherlands.

Previous analyses haven’t agreed on whether online or in-store shopping is better. In fact, some studies have found that online shopping has a lower impact, because it saves the emissions associated with driving your car to the store (95 percent of Americans drive to go shopping). But this benefit can vary, or even disappear, depending on how fast we want that TP to arrive. And if you’re shopping in real life, factors like how you transport those items, how far you travel, and how much you buy at once all affect the carbon footprint of your purchase. “There have been some contradicting results, with some saying online shopping is better and some saying traditional shopping is better,” says Sadegh. So he tried to settle the debate with an approach that showed how likely one option was to be better than the other.

Sadegh and his team compared three shopping styles: traditional in-store shopping, online ordering from a physical store (which they called “bricks and clicks”), and ordering through an online-only retailer. Nearly two-thirds of the time, bricks and clicks shopping resulted in fewer emissions per item than in-store shopping — and was better than online shopping 97 percent of the time. In-store shopping had fewer emissions than online — only 81percent of the time.

9 . Commercial aviation (航空) alone contributes around three percent of total global carbon emissions (排放). But the industry is actively looking for green solutions in the form of sustainable aviation fuel (SAF). In a study released this week, a team of researchers from the U. S. Department of Energy’s National Renewable Energy Laboratory (NREL) details a method of transforming food waste into SAF that can be used in existing engines. Making SAF is a more complicated process—it’s got to be very similar to the petrol-based aviation fuel we use today in commercial flights.

The researchers use volatile fatty acids (挥发性脂肪酸)(VFAs) from smelly food waste and transform it into simple paraffin molecules (石蜡分子) that can be used in fuel and really aren’t all that chemically different from traditional emissions-heavy fuels. There are other renewable biofuels that have been made from biomass (生物质), specifically oil and fat from vegetables and animals, but using the ever-mounting pile of food waste to fuel flights broadens those possibilities.

Derek Vardon, a senior research engineer at NREL, says major companies are eager to get involved in SAF because some sustainable solutions, such as battery-operated commercial flights, just aren’t possible yet with current battery technology. A battery-powered plane would be too heavy to fly long distances—“So using SAF that works in the same way as the fuel we have is a simpler way to trade out traditional emissions-heavy fuels.” Vardon also says that “because the wet waste would normally go to a landfill and break down to release greenhouse gases, the process of making and using SAF could actually have a negative carbon footprint when it is dramatically used.”

A major question as the researchers move forward with this type of research is if it is possible to run an airplane engine on fully renewable biofuel. Rolls-Royce recently did a test on one of their engines with 100 percent SAF and it worked. “This fuel is not crazy and we can solve these problems,” Vardon says.