For more than 100 million years sea turtles (海龟) have covered huge distances across the world’s oceans, making them among the oldest creatures on the planet. However, they are on the list of endangered species.

Different from some animals like snakes, the sex of the baby sea turtles, called hatchlings, is determined by the environment after fertilization (受精). The temperature of the eggs during a certain period of development is the deciding factor in determining sex, and small changes in temperature can cause very big changes in the sex ratio (比例). Often, eggs at low temperatures (22—27℃) produce males, while eggs at higher temperatures (30℃ and above) produce females. At temperatures in between, both sexes will be produced. If temperature reaches 36℃, no hatchlings will be produced.

Climate change has a powerful effect on turtle nesting (筑巢) sites. It changes sand temperatures, which then affects the sex of the hatchlings. Scientists have found that unusually warm temperatures caused by climate change are upsetting the normal ratios, resulting in fewer male hatchlings. The past four hottest summers in Florida have seen only female sea turtles. And an Australian study has shown a similar effect in which 99% of the hatchlings are female.

In addition to rising temperatures, turtles are also facing the threat of too much plastic in the oceans, along with a number of other threats. “Plastic pollution is a problem for turtles as they can mistake plastics for food easily. Even a single piece of plastic can kill a turtle,” Dr Couper, working at the Queensland Museum, said. “We have collected some plastics taken from turtles’ stomachs to show people what kinds of things are showing up on beaches. I want it to be an eye opener.”

Bird migration is described as the regular, seasonal movement of bird populations from one place to another and back again.

The longer days and rich food of the northern summer provide greater chances for birds to feed their young. The longer daylight hours and enormous food resources allow birds to lay larger eggs than those of related non-migratory species that remain in the tropics all year round. As the days shorten in autumn and the breeding period is over, the birds return to warmer regions where the available food supply differs little with the seasons changing. The advantages of migration make up for the high stress, physical exertion（消耗）, and other risks of the migration.

Day length is the primary environmental factor that encourages birds to prepare for migration. They have an increased appetite which results in weight gaining, giving them the fat reserves that provide energy for their migratory flight. They also show more activity at night, which is when most birds migrate. While the length of day is the primary reason for migration, birds also respond to temperature changes. For example, if a spring is late and the temperature is lower than normal, birds delay migration; if a spring is early, birds also begin migration early.

The timing of the migratory cycle must allow birds to arrive on the breeding site so that there is time to build a breeding place, mate, lay the eggs, and hatch the young before the rich food is available to feed the young in the nest. Similarly, if birds wait until the climate in their northern breeding grounds becomes tolerable(可忍受的), there will be no time to gain the necessary weight that provides the energy needed for their southbound migration.

A new study recently found that elephants in central African forests can encourage the growth of slow-growing trees and increase the ability of the forest to store carbon.

“As a tree, there’s a trade-off you can’t have it all,” explained Fabio Berzaghi, who led the study. “You either invest in growing fast, or in building a lot of structure with carbon to be more resistant.” Elephants prefer to eat fast-growing trees in more open spaces. As they feed and walk, they cause damage to these species, knocking over trees or breaking off branches, which results in an ecosystem that favors large, slow-growing hardwood trees. “As the elephants thin the forest, they increase the number of slow-growing trees and the forest is capable of storing more carbon, ” said Stephen Blake, one of the paper’s authors.

Scientists collected field measurements in the Congo Basin and used a computer model to predict how elephants would affect forest structure, and carbon storage potential in the long term. The data confirmed that when elephants are present, the forest contains larger trees and higher abundances of species with high wood density. Conversely (相反地)，should forest elephants go extinct, leaving those slow-growing trees struggling to compete with fast-growing species, it would result in a 7 percent loss of above-ground biomass (生物总量). As a result, central African forests could lose up to three billion tons of carbon, potentially accelerating climate change.

The sad reality is that humans are doing their best to rid the planet of elephants. “This study comes at a time when forest elephants are threatened as never before,” said Iain Douglas Hamilton, founder of Save the Elephants. “It is shocking that just as we are beginning to understand how elephants might have a key role in Africa in storing carbon, they are under real threat of extinction.” One limitation of the study, Mr. Berzaghi said, is that we do not know how much carbon has already been lost because of the elephants’ decline. But it does seem certain, he added, that putting a stop to illegal hunting and restoring forest elephant populations would bring climate benefits.