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Over the past 125,000 years, mammals on Earth have become smaller. Ten thousand years ago the average mass of a mammal was 200 pounds and today the average mass is about 15 pounds. After dinosaurs became extinct, mammals became larger and new species developed. But when ancient humans evolved, they began hunting bigger animals. Eventually, in all areas populated by humans, the size of mammals became smaller and led to extinction in many cases. Listen to hear more about the effects humans have had on the size of mammals.

Researchers have completed a study that documents the environmental impact of producing a loaf of bread. They determined the amount of greenhouse gas emissions at each stage of bread production—from wheat farming to transportation—and added up the total. They found that 2.6 million tons of greenhouse gases are emitted each year in the U.K. as a result of bread production. The study’s authors hope the findings will lead to more efficient and sustainable production methods. Listen to learn more about the environmental footprint of a loaf of bread and how consumers can help make a difference.

The latest research shows that humans are the leading cause of wildfires in the United States. As global warming leads to longer fire seasons and larger wildfires, human activity is causing wildfires to happen at times of the year when they would not be happening naturally. Human activity has also extended the normal fire season in the U.S. by three months, and ecologists worry that without action taken on this issue, wildfires will become even larger and more frequent. Listen to learn more about humans’ role in increasing wildfires, and what ecologists believe must be done to reverse this trend.

A week of high pollution levels in Paris has brought strict restrictions on driving. The Paris mayor is making public transportation free in an effort to reduce the pollution particles in the air. There are also health concerns if people breathe this air for more than an hour, so some school sports and outdoor activities were banned temporarily. Listen to hear more about how Paris is managing this pollution crisis.

Beginning 200 years ago, many of Vermont’s rivers were straightened for agriculture, logging and to power turbines. Today one of three river miles in Vermont has been straightened, causing the waters to run deeper and faster – and erode away people’s property and roads. Vermont has experienced three 100-year floods in the past 30 years. Traditionally, the state and property owners have built expensive barriers to keep the rivers in line. Now the state is thinking about taking a new approach to floods: creating zones along the riverbanks where no new construction is allowed to let the rivers flow where they naturally want. Listen to this VPR News story and then use the questions below to discuss the issues it raises.

Two recent incidents at Yellowstone National Park highlight a problem. In one incident, visitors walked off the boardwalk at a hotspring, and in another, visitors put a bison calf in their trunk to keep it warm. There are record numbers of visitors to National Parks and educating them all about wildlife and safety is a huge task. Regardless of visitor’s intentions, park officials are hoping to reduce the numbers of incidents. Listen to hear more about managing visitors’ behavior at National Parks.

Every spring and fall Americans turn the clocks back or forward one hour to make the best use of the daylight. It’s called Daylight Savings Time. When the clocks are turned back in the fall, it will be brighter in the mornings as we go to school and to work. New research shows this time change has a big downside: an increase in crime. By looking at crime patterns, researchers discovered that robbery rates increase when it's darker for a longer time in the evenings. Listen to this story and have students gather evidence for a debate about whether or not we should keep Daylight Savings Time.

The Amazon in the north of Brazil is being deforested, and it is estimated that 80% of the wood harvested is illegal. Many environmental groups are fighting deforestation on the basis of its effects on global warming. But there’s one group of indigenous people in Brazil is fighting back against illegal loggers. This tribe is trying to preserve the trees because they are central to their way of life. They surround and warn illegal loggers and then drive them away with bows and arrows. There are many other issues with big business and corruption that affect this forest. Listen to this story to hear about some local efforts to protect the Amazon Forest.

Peregrine falcons are making skyscrapers in many large cities their new homes. By living in urban areas and nesting on tall bridges and skyscrapers instead of cliffs, they have plentiful food and safe nesting areas. In Massachusetts, there are now about 35 pair of these previously endangered birds, more than there have ever been. The population rebounded after the birds shifted their habitat. Some are nesting in skyscrapers in downtown Boston. Listen to this story about three fledgling peregrine falcons who are learning to fly from their nest on the 19th floor of Boston University housing tower.

When did humans begin to shape the earth? This is the debate happening among geologists who are determining whether the official timeline of the Earth should have a name for the current period of human domination. The concept of the “anthropocene” or the human era first emerged 15 years ago and a working group of scientists is determining whether to adopt it officially and when it should begin. Listen to learn more about the lively debate that surrounds this decision.