Costa Rica has a long-standing commitment (投入) to the environment.【小题1】It has doubled its forest cover across the country in the last 30 years.

In the 1940s, more than three-quarters of the country was covered in mostly rainforests and other woodlands. Then, between the 1940s and 1980s, heavy, uncontrolled logging (伐木) led to serious deforestation (滥伐).【小题2】Realizing the great damage that was happening, government officials took a stand. Through a continued environmental focus, they were able to turn things around to the point that today forest cover has increased to 52%, which is double that of 1983 levels. That forest cover is able to take in a huge amount of CO₂from the atmosphere, fighting climate change for us all.

【小题3】The government encourages landowners to protect the land through cash payments if they sign contracts (合同) with the Ministry of Environment. These contracts allow the landowners to take only a certain number of trees from the forest, and also require that they continue planting trees in the deforested areas.【小题4】

Robert Blasiak, a researcher at the University of Tokyo, said, “Taking a closer look at what Costa Rica has achieved in the past 30 years may be just the driving force needed to make real change all over the world.”

That is exactly what the Costa Rican leaders hope to achieve.【小题5】The Costa Rican President has called the climate crisis (危机) “the greatest task of our generation”; one that his country is strongly committed to.

In this Pennsylvania city, Pittsburgh is shrinking but getting wealthier. Since 2000, its population has declined by 95,000 while its income per capita (人均) has shot up 24 percent. The trend is taking hold in many other cities, like Buffalo in New York, Providence in Rhode Island and New Orleans.

Some of these areas have created more high-paying jobs in energy, health care or education. Others have managed to reshape their producing industry for a new economy. Higher-paying jobs have a greater effect because they create demand for additional services. "The story in Pittsburgh is very positive, and other areas are looking at it as an example of the transformation that might be possible,” said Guhan Venkatu, who wrote an economic history of the area called “Rust and Renewal” for the Federal Reserve Bank of Cleveland.

Carnegie Mellon University and the University of Pittsburgh have helped bring tech jobs and innovation(革新) to the area by sponsoring tech centers that help graduates start companies without moving to Silicon Valley or San Francisco. This has helped keep Pittsburgh's educated young population growing even as the entire population in the city has dropped.

Pittsburgh has more STEM (science, technology, engineering and math) jobs than other shrinking cities, about 80, 000 or 7% of all jobs. STEM jobs add productivity and income growth to the area. Manufacturers of high-tech medical equipment in the Pittsburgh area also have doubled employment in the last 10 years.

However, some experts question whether growing income per capita can really make up for a declining population. According to Patrick Adler, a researcher at the University of Toronto, population loss does matter if it means lower-skilled workers have fled because of a lack of opportunity. What's more, high-paying jobs in education and health care can disappear if the population declines too greatly. So it'd be wise to find ways to increase the population.

The month of March was a milestone for supporters of renewable energy in the U.S. For the first time, wind and solar power accounted for more than 10% of the country’s electricity—up from less than 1% at the turn of the century. And total wind and solar power-plant capacity(发电量) is expected to grow more than 30% over the course of this year and next, according to the Energy Information Administration.

Such forecasts have led many scientists and policymakers to think that moving a large part of the nation’s power supply to renewable sources—as cities from Miami Beach to Salt Lake City have promised to do—may not be as far-fetched as once thought. But like any debate, there are dissenters, including those inside the federal government. Their argument is that the nation demands an uninterrupted supply of electricity and cannot count on sun, wind and natural gas to provide it. “You need solid hydrocarbons(固体碳氢化合物) on-site for rising peak demand,” Environmental Protection Agency administrator Scott Pruitt said on Fox Business in May, referring to the importance of coal as a power source.

Many experts say the government’s concern fails to account for how the power grid(电网) has improved in recent decades. Utility companies(公共事业公司)

have developed innovative ways to move electricity from place to place to account for variation in weather. Battery technology can store power for use when renewable sources cannot operate, meaning solar power can be used on days when the sun doesn’t shine. And the nation’s vast supply of natural gas can be turned into usable energy with the flick of a switch.

“I don’t think 5 or 10 years ago I’d be comfortable telling you we could not sacrifice reliability when we’re going to have 35% of our energy come from wind,” said Ben Fowke, CEO of the utility company Xcel Energy, at a recent conference. “I’m telling you, I’m very comfortable with that today.”

Indeed, many parts of the country are already close to that reality. In some regions, like Iowa and Kansas, renewable energy supplies more than 25% of the electricity. The market has shifted so far in favor of natural gas and renewable energy that even the most concerted federal effort is unlikely to stop its growth. Any attempt to slow the growth of wind and solar will face strong pushback. “If anyone wants to do away with it,” Republican Senator Chuck Grassley told Yahoo News of the federal government’s potential cuts to wind energy, “he’ll do it over my dead body.”

But the federal government could slow the acceleration—and with billions of dollars in private and public investments at risk, the pace of change matters. Decisions made today will shape the future of the nation’s energy grid for decades to come.