Fresh Science: Spring arrives early and disrupts the world

Spring is coming earlier

Spring is coming earlier and earlier. In April 2016, monitoring by the National Climate Center showed that spring arrived earlier than usual in most areas of central and eastern my country, with the eastern part of North China arriving about 10 to 20 days earlier and the Jiangnan region more than 20 days earlier. And the temperature is also higher than the same period of the year, about 2℃~4℃ higher.

The same is true on the other side of the world. According to the latest observations, this unusual weather phenomenon also occurred in the United States in late February 2017. Temperatures in the eastern United States have skyrocketed, with temperatures in many cities soaring to more than 20 degrees Celsius, and some even rising to 34 degrees Celsius, which is the highest February temperature in the eastern United States since temperature changes began to be recorded in 1871.

This means that winter has come to a "strange" end, but what is even stranger is that at the same time, the western United States has experienced colder weather, and California has experienced record highs in rain and snow precipitation. Annual snowfall in ski resorts in the Sierra Nevada exceeds 12,700 millimeters, breaking a half-century record. In fact, it’s not that the west is colder, but that the east is warming up earlier.

For most parts of the United States, early warming means early entry into spring. In 2017, some people predict that tree buds and flowers may bloom earlier. The famous cherry blossoms in Washington, D.C., bloom two and a half weeks earlier than in previous years.

According to the United States Geological Survey, spring has entered in early March in most areas of the southern United States. In the statistical map released by it, spring is 20 days earlier than usual in the areas represented by dark maroon.

Disrupting the tourism industry

Although "Spring in February" brings "jasper" and "green silk ribbons" and revives all things, it does not mean that the earlier spring comes, the worse people's lives will be. The better. When the temperature changes untimely earlier, it means that the seasonal change is also somewhat untimely.

In fact, the early arrival of spring does not occur regularly, but changes year by year. Maybe one year the cherry blossoms bloom three weeks earlier than previous years, and the next year they bloom one week later. Plants bloom at different times each year, but generally they bloom earlier and earlier. Therefore, it is difficult for people to predict the date when spring will arrive each year.

The most intuitive impact is on the tourism industry, because any outdoor activities or large gatherings must consider weather changes, especially in the cold spring. Take cherry blossom viewing for example. The blooming period of cherry blossoms only lasts about 10 days. If you cannot predict the arrival time of spring, you cannot organize a flower viewing tour in advance.

There is a very unique type of firefly in the Great Smoky Mountains National Park in the central United States, called the synchronous firefly. There are more than 2,000 species of fireflies in the world, but only some of them have the ability to emit light, and among all the glowing fireflies, only a handful emit light simultaneously. The fireflies in the Great Smoky Mountains are this rare species, so many people travel to the Great Smoky Mountains every spring, hoping to see a large number of fireflies glowing simultaneously. For the Great Smoky Mountains tourism managers, they need to arrange food, accommodation, transportation and other issues in advance. However, the arrival time of spring has been extremely unstable in recent years, making advance arrangements very difficult. Meteorological spring and phenological spring

In fact, what people usually call spring includes two aspects. On the one hand, it refers to meteorological spring, that is, the daytime temperature begins to rise, the nights are no longer so cold, and frost no longer forms on the ground; on the other hand, it refers to phenological spring, that is, everything revives, plants sprout and bloom, migratory birds return north, insects are active, and many Animals begin to lay eggs, hatch and give birth to offspring.

Usually, the two aspects of spring complement each other and occur simultaneously. When the temperature rises early and meteorological spring arrives, if the phenological spring is not synchronized, it will disrupt the physiological mechanisms of animal and plant growth and reproduction, and may even affect the earth's ecosystem.

A variety of measurements show that meteorological spring is coming earlier and earlier. In the Northern Hemisphere, the first warm wave in early spring arrives about one day earlier every decade, and the last cold wave in winter also comes earlier and earlier. According to a recent observation, more than three-quarters of national parks in the United States experienced an earlier-than-usual spring.

Meteorological spring has come early, has phenological spring also come early? In terms of agricultural planting, compared with the 1960s, the planting time in most areas of the United States has advanced by one week. The budding time of trees is also one day earlier than 10 years ago. Some are synchronized, but some are not.

Asynchronous occurrence disrupts the ecosystem

When the meteorological spring and the phenological spring do not match and are not coordinated, the lives of animals are most vulnerable to interference, and their physiological mechanisms for survival and reproduction are will be disordered. The most obvious manifestation is that in the Arctic region, with the arrival of early spring and the melting of ice and snow, some grasses will germinate and bloom one month earlier than usual. However, hibernating animals later wake up "on time" and will find that some very important early spring is missing. food sources.

Also, snowshoe hares will change the color of their fur to protect themselves. It turns white in the winter and brown in the summer, which is a good protective color. But when the snow melts early, many rabbits are unable to moult in time, so they still have conspicuous white fur on the brown soil in spring, making them easy to prey on.

What is even more destructive is that meteorological spring has arrived early, but not in all aspects.

For example, frost is a natural phenomenon that occurs when the surface temperature drops suddenly below 0°C. When spring comes and the temperature rises, it will end. The last frost is called final frost. However, American scientists have found that the date of the last frost in many places in the United States remains unchanged. This seems to be related to the early spring lasting too long.

In some higher elevations in the American Rockies, the last frost date usually remains June 10, even if early spring arrives earlier. Generally in late May, the snow in the mountains will gradually melt, and wildflowers usually start to grow at this time, and flower buds will appear in about a month. This is just the right time to avoid the final frost, allowing the delicate buds to truly enter spring. But now the snow begins to melt in mid-April, and wildflowers grow early, but the final frost does not end early. As a result, some flower buds did not survive the frost period and were frozen to death. This means that in the future there will be no nectar, no pollen for insects to spread, and no seeds for animals to use as food, then the ecosystem will be seriously disrupted.

Looking for coordination between ecology and climate

There are also some plants that are not affected by meteorological spring, such as broad-leaved trees in high latitudes in the north - oak, beech, hackberry, etc. These broad-leaved trees will not start to grow and sprout as the temperature rises. They need to wait for the arrival of astronomical spring before they will bloom and bud. (Astronomical spring refers to the vernal equinox, when the sun shines directly above the equator). Broadleaf trees will also experience the annual final frost, but they will not be misled by the "false" temperature rise in early spring, because they still need winter sunlight (the sun slants in the northern hemisphere in winter, and the intensity and effect of the light are completely different from direct sunlight in summer) . Scientists have found that even if these broadleaf trees are planted further south, they may thrive in February, but the degree of light tilt will still depend on the degree of light exposure, and they will never bloom until near the vernal equinox.

It is undeniable that spring has indeed advanced now, but it has not advanced simultaneously in all aspects. This has caused chaos in the earth's ecosystem and also brought many uncertainties to human life. If scientists can figure out the secret of how open-leaf trees use light as their flowering standard, perhaps we can find effective ways to deal with this irregular seasonal change in early spring. Of course, more importantly, we should also be friends with nature, not emit too much greenhouse gases, and try to avoid spring arriving early.