5 . Tropical (热带的) forests could become so hot that some kinds of leaves will no longer be able to conduct photosynthesis (光 合 作用), according to a study. The photosynthetic machinery in tropical trees begins to fail at about 46.7℃ on average. The research suggests that forests may be nearing dangerous temperature sooner than expected. Models predict that once we hit a global temperature increase of 3.9℃, these forests might experience mass leaf damage.

Chris Doughty, an associate professor at Northern Arizona University and the lead researcher of the study, said the leaf-warming experiments had revealed a nonlinear rise in temperatures. “We were really surprised that when we warmed leaves by 2, 3 or 4℃, the highest leaf temperatures actually increased by 8℃. This shows a concerning nonlinear feedback that we were not expecting.” said Doughty. “If we adopt a do-nothing response to climate change and tropical forest air temperatures increase by greater than 4℃, there could be massive leaf death.” he added.

Avoiding high emissions (排放) in the first place is key to stabilizing temperatures. “We should do all we can to avoid high-emissions. Under low-emissions, almost all tropical forest tree leaves can avoid death from overheating and the trees will survive,” said Simon Lewis, a professor of global change science at University College London. “Yet what the study doesn’t look at is heatwaves. We still might see tree deaths from overheating for limited periods during heatwaves under lower emissions.”

Researchers suggest that the damage is not yet unchanged. “Vote for people who are serious about addressing climate change and transferring to low-carbon economies, ”Disney, one researcher, advocated. More generally, we can all recognize the importance of supporting those countries and people who live in and rely on tropical forests economically, But the serious changes to tropical forests don’t just affect the local people it’s a global issue.

7 . Earth Hour is an annual event, asking you to switch off all your lights for one hour in positive change for our planet. It is organized by the World Wide Fund for Nature and it’s a big event usually at the end of March every year.     1    , which means switching off all lights everywhere at the same time for one hour.

Earth Hour started in Australia in 2007, when 2.2 million people in Sydney turned off all unnecessary lights for an hour.     2    , and many countries around the world have taken part.

It’s true that switching off the lights for just one hour saves only a little power.     3    . Joining in Earth Hour makes people think about the problem of climate change and how to protect nature so that people can enjoy healthy and sustainable lives. Besides, many people acting together pushes governments and companies to consider green issues when making big decisions.

    4    . The number 60 is for the 60 minutes of Earth Hour, and the plus invites people to keep on taking action even after Earth Hour is finished. In fact, people joining in Earth Hour say that taking part in it inspires them to do more for the environment. The climate activist Greta Thunberg says, “Earth Hour is every hour of every day.”

Why is it in March? At the end of March in the northern and southern hemispheres (半球), the days and the nights are almost of the same length.     5    , so it is dark in the evening in each country for the Earth Hour switch-off.

Xixi, located less than five kilometers from the West Lake in the west of Hangzhou, is China’s first national wetland park. The area covers about 10 square kilometers and it     1     (be) around for more than 1,500 years, although it was only recently reopened     2     (offer) visitors a chance to escape from the concrete of the city. Despite its growing popularity,     3     wetland’s winding waterways, thick greenery and wide     4     (variety) of wildlife guarantee its peaceful spots in nature.

Wetlands themselves are one of the most biologically diverse ecosystems,     5     (act) as natural green lungs, water purification (净化) systems and flood control. But wetlands are     6     (serious) threatened by environmental pollution worldwide nowadays. More than 200square kilometers of wetland in the country have disappeared every year     7     average in the past decade, the China Institute for Marine Affairs warns. The wetlands of the Yellow and East China seas have lost up to 90 percent of their natural function, the institute reports,     8     makes the 226 plant species, 50 kinds of fish and aquatic (水生的) animals as well as 126 kinds of birds in Xixi even     9     (valuable).

Xixi’s native vegetation,     10     (water) by six crossing rivers, consists of subtropical mountainous swamp (沼泽) and evergreen forest.

9 . When scientists and the public worry about sea level rise, they mostly focus on when and where communities will be permanently flooded. But there’s another consequence of rising seas that will affect many more people much sooner: getting cut off from roads and other critical infrastructure (基础设施). It’s a threat that society has not paid nearly enough attention to, says Allison Reilly, a civil engineer at the University of Maryland.

In a new paper, Reilly and her colleagues show the width and pace of the isolation (隔离) threat. Inspired by her work on the eastern shore of Maryland, where people already need to adjust their travel and work schedules to account for tides that frequently flood roads, Reilly and her colleagues calculated that, with one meter of sea level rise, twice as many people across the coastal United States will be isolated than will be fully flooded.

Worse still, many places currently considered at low risk of sea level rise suddenly become much riskier when isolation is taken into account, Reilly says. While planners know that low-lying Florida will be severely flooded, Maine, with its high rocky coasts, is generally thought to be at low risk. But Reilly’s work shows many Mainers are in great danger of being cut off by flooding in coastal communities and river valleys.

This far more immediate effect of rising seas needs to become part of the broader planning process. That kind of planning is starting to happen around the Chignecto Isthmus, an interprovincial land bridge in Canada, connecting New Brunswick and Nova Scotia. The New Brunswick and Nova Scotia governments are considering a variety of plans to raise or replace the dikes (坝). For Ollerhead, a Nova Scotian, that work can’t start soon enough. “It will take a lot of sea level rise before Nova Scotia becomes an island, but you could have a storm that cuts off the major transportation links for days, weeks, or months,” he says. “It’s nearly impossible to predict when, but it will happen eventually.”