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One article per day for Global Humanities and Geography
WeChat public account: Earth Knowledge Bureau
NO.2678 - No.2678 -
Text: The sound of grass and trees in the woods
Proofreader: Kelsey / Editor: Clear
Special thanks to: Associate Professor Yu Le, Department of Earth System Science, Tsinghua University
The steppe, the endless steppe, is the intuitive imagination of the Chinese for thousands of years of inland nomads in Asia, after all, this is the world's largest grassland belt, stretching from the Great Khing'an Mountains all the way to Hungary, giving birth to countless nomads, staging countless conquests and migrations.
But in the era of industrialization, dramatic increases in grazing and unreasonable reclamation have greatly damaged the grasslands. On the one hand, this is a heavy blow to the nomadic economy, and on the other hand, it has also pushed those areas that depend on grassland ecology to the brink of life and death.
▲ Caption: What do you imagine?
(Photo: Yitu.com)
▲ Caption: In fact, many of them have changed color
（图：shutterstock）
But according to a recent study by the Department of Earth System Science at Tsinghua University, in this century, the grassland area of the entire Eurasian steppe has expanded!
What's going on? After all, the Eurasian steppe is very huge, and the expansion of the total amount does not mean that the parts are all beautiful stories. Especially within different national borders, the fate of the grasslands is also inseparable from their respective national fortunes.
▲ Caption: Aral Sea, highly agreed
(Dry Aral Sea Photo: Yitu.com)
grass, the gap between rich and poor is also serious
The formation of grasslands is closely related to the climate, and tall trees need sufficient moisture to nourish them. As a result, grasslands around the world are mostly distributed in areas with low precipitation. In areas where the alternation of wet and dry is evident and there is plenty of heat, savannahs are formed. For example, the African savannah, where giraffes and hippos live.
In Asia, the uplift of the Tibetan Plateau has changed the distribution of pressure zones, and the monsoon carries water vapor deep into the eastern and southern parts of Eurasia, creating the most densely populated region in the world.
▲ Caption: Asian Monsoon Zone:
In terms of population density, everywhere else is scum
(Landscape World Population Density Chart)
▲Caption: Zoom in to take a look
The population density in the South Asian monsoon region is particularly striking
(Photo: reddit.com)
However, the hinterland of the Eurasian continent is too vast, and the pace of water vapor is limited after all, so in the interior of the largest continent in the world, the world's largest temperate grassland was born.
Such a steppe belt is too large, spanning thousands of kilometers from the Carpathians to the Great Khing'an Mountains, and the interior is naturally very different.
▲ Caption: Super steppe, across the Eurasian continent!
(Horizontal screen, aerial view of Eurasia, Photo: Yitu.com)
Water is always the most important influencing factor in grasslands, and at the edge of the grassland or in places with high mountains in the background, relatively abundant water vapor and rivers flowing from the mountains will create wetter and more fertile grasslands.
If there are warm summers and cold winters, a large amount of humus will gradually accumulate, forming extremely high-quality land - chernozem. Hulunbuir, with its abundant water and grass, and the black soil of the southern Russian steppe - Ukraine belong to this category.
▲ Caption: Mention of black soil
The Northeast has to come in and nag
▲Caption: On the fertile black soil
Nearly one-fifth of the country's food is produced every year
(Photo: Picture Worm Creative)
Most of the area of the Eurasian grassland belongs to the dry grassland, and the xerophytic perennial grasses mainly grow on the chestnut lime soil. Except for those grasslands that have become tourist areas due to their beautiful scenery, most of the grasslands that can maintain a certain intensity of grazing are of this type.
▲Caption: The prairie is so rich in aquatic plants
In fact, it is rare
(Mongolia steppe Photo: Onemap.com)
In areas deep into the hinterland where precipitation is scarce, the grass will appear dry and can only support low-intensity grazing. Even a little more livestock can lead to severe grassland degradation.
▲ Caption: Such a withered and yellow degraded grassland
It's the daily life in most areas
(Mongolia steppe map: Yitu.com)
Grassland, different national fortunes have different fates
The world's largest grassland belt is spread across more than a dozen countries and is divided by straight or curved borders. At opposite ends of different borders, the fate of the land is also very different. For example, at the junction of China, Russia, Mongolia and Kazakhstan, it is one of the hubs of the steppe belt - the Altai Mountains, and in different directions, the steppe belt presents different appearances.
▲ Caption: A mountain has four seasons, ten miles of different days
The Altai Mountains, which straddle the borders of Shikoku, have a variety of landscapes
Forests, grasslands, oases, snow-capped mountains, and the Gobi are all there
In a recent study by Tsinghua University's Department of Earth System Science, the most significant increase in the Eurasian steppe came from Kazakhstan, a country with a long tradition of pastoral farming, to be exact, large swaths of abandoned farmland in the former Soviet Union.
▲ Caption: Kazakhstan today
About 76.1% of the land belongs to the sensitive areas of moderate or above desertification
The ecological environment is facing severe challenges
In 1954, in order to solve the already problematic Soviet agriculture, Khrushchev, who was engaged in agriculture, took a fancy to the North Kazakh steppe, which was at a similar latitude to Ukraine, where he was prosperous. Since the South Russian-Ukraine steppe can be reclaimed into a world-class granary, then Kazakhstan should be able to do the same.
▲ Caption: Such an arid climate is engaged in reclamation
It's really not a good idea
(Farmland in northern Kazakhstan Photo: Onemap.com)
After the call was issued, a large number of young people rushed to the "virgin land" in northern Kazakhstan to carry out reclamation work. Farms are springing up. Grain production in the USSR rose rapidly.
But the Kazakh steppe is too inland, and the scarce water vapor and poor soils cannot support sustained large-scale extensive agricultural activity. Only a few years later, by the 60s, black storms began to sweep through Central Asia, and the ecosystem was in jeopardy.
▲ Caption: Whether it is a black storm or a sandstorm
These are all ecological disasters caused by over-cultivation
(Sandstorm Photo: Yitu.com)
If this trend continues, Kazakhstan today could be seriously dragged down. Fortunately, the rich oil and gas resources of the Caspian Sea have allowed Kazakhstan, which has a small population, to live a good life, and those reclaimed "virgin lands" have been abandoned.
▲ Note: Don't look at the old equipment
The oil pumped out is real
(Kazakhstan oil field Photo: Google Maps)
▲ Caption: The rolling oil wealth poured into Kazakhstan through the oil and gas pipelines
(Kazakhstan Oil and Gas Pipeline Photo: Shutterstock)
Nature's power of restoration is quite powerful, and in just a few decades, a considerable amount of abandoned arable land has been restored to grassland under secondary succession. Although the ecological situation in Central Asia is still not optimistic, it is much better than Mongolia on the other side of the Altai Mountains.
▲ Caption: Sheep: My home is back
(Grassland near Almaty Photo: Yitu.com)
The study by Tsinghua University found that the grasslands of southern Mongolia have become the most severely degraded areas in the entire Eurasian steppe (strictly temperate semi-humid semi-arid, arid steppe zone). The situation in the southern provinces named after the Gobi will only get worse.
▲ Note: Desertification in southern Mongolia is particularly shocking
In fact, the study found that human activities associated with urbanization and its expansion are highly correlated with grassland degradation, and Mongolia has one of the lowest population densities in the world, with only a population of just over 3 million people in a territory of more than 1.5 million square kilometers, half of which live in the capital Ulaanbaatar, and the rest of the country is almost uninhabited. This level of land degradation is also due to overgrazing.
▲ Caption: Except for Ulaanbaatar
There are few people in the rest of Mongolia
During the Cold War, Outer Mongolia was an important animal husbandry base of the Soviet Union. The nomadic way of herding that used to allow the grasslands to rest has also been changed to grazing on fixed pastures. The soil thickness of ordinary grasslands is about 10 centimeters, while the Gobi steppe of Mongolia, located in the hinterland of the Eurasian continent, will only be more fragile.
▲ Caption: I can't bear so many sheep
（图：shutterstock）
Kazakhstan and Mongolia, the steppe stories of these two neighboring countries, have also been played out in China to a greater or lesser extent. In this study by Tsinghua University, it was found that there is also a lot of abandoned/abandoned farmland in China that has been converted into grassland. This is not nature's correction of people's blind cultivation in the past.
▲ Figure note: In our dividing line between agriculture and animal husbandry, the precipitation is still relatively low
To meet the needs of 1.4 billion people, this is not enough
Of course, the overall growth of the Eurasian steppe does not mean that the problem of degradation is solved. Around Hohhot and Astana, the capital of Kazakhstan, some of the largest cities in the grasslands, urban sprawl has led to grassland degradation. Many forests in Eastern Europe have also been degraded to grasslands.
▲ Caption: Compared with Astana, Ulaanbaatar is the burning eyebrows
Grassland degradation has led to an influx of poor herders to Ulaanbaatar to earn a living
The hillside is crowded with dense "Mongolia bags"
It can be said that it is a slum with Mongolia characteristics
Changes in the natural world are extremely complex problems, and not a single single tree can solve everything. The protection of ecosystems begins with a full understanding of it.
▲Caption: Ecological governance is essentially a social and economic issue
Ulaanbaatar is full of slums + low-quality loose coal for heating
The ecological environment has long since collapsed
(Ulaanbaatar Photo: YITU.com)
Capture the glimmer
You must know that the entire Eurasian steppe spans nearly 7,000 kilometers from east to west, and a few decades ago, it was almost impossible for human beings to know the whole and state of this huge steppe.
This kind of observation can only obtain a part of the point data, and the data update is quite slow. China's first nationwide grassland survey began in 1979 and was completed in 1987 with almost all the manpower and material resources of related disciplines.
▲ Caption: It is not easy to come by
It took nearly ten years, and the relevant manpower and material resources were exhausted
Finally, this map of China's grassland resources has been completed
The higher you stand, the farther you can see. Although satellite remote sensing cannot completely replace field work at present, the perspective of satellites and the grand observation object are indeed highly compatible.
At a glance from the sky, you can observe the changes in this land as a whole. As for some of the more detailed work, it can be done by drones.
▲ Caption: A large sandstorm is blowing
It's all visible in space
(East Asian sandstorms Photo: NASA)
The green earth seen by satellite remote sensing is, in the final analysis, the color of countless plants themselves. But in addition to the colors that are visible to the human eye, there are also parts that we can't see.
For example, seasonal changes can cause discoloration of leaves and grasslands, but this is not necessarily noticeable at high altitudes. This is where the invisible hyperspectral comes into play: when plants photosynthesize, they mainly absorb red and blue light and reflect green and infrared light.
Under the spectrometer of remote sensing satellites, there will be a significant difference in the vegetation coverage area in the infrared and near-infrared bands. The absorption of red light by different plants and at different growth stages of the same plant will also be slightly different.
▲Note: The spectrometer collects a large number of data in different bands
Depending on the object of study and observation
Export the data for the corresponding band
The corresponding satellite remote sensing map is then generated
(Schematic diagram of the spectrometer: NASA)
But the physiological and ecological changes in plants are often very subtle, so scientists have focused on even fainter light - the faint fluorescence emitted by chlorophyll a in the light of excitation.
Chlorophyll a plays an important role in photosynthesis to collect light energy and convert it into chemical energy to decompose water to release oxygen. If you can monitor chlorophyll fluorescence, you can understand the strength of the entire photosynthesis. This glimmer of light, which was once only observed under a microscope, can now be monitored with satellites.
▲ Note: Chlorophyll fluorescence is the light emitted by plant growth
Known as the ideal "probe" for plant photosynthesis
It can accurately reflect the real working state of plant photosynthesis in a timely manner
In this way, we can interpret the changes in the size of global vegetation from it using a reasonable inversion model. In modern remote sensing, scientists use the resulting "NDVI index" to analyze the distribution of vegetation.
▲Caption: NDVI is also called "Normalized Vegetation Index"
As complicated as it sounds, it's all about monitoring the growth of vegetation
The greener the place looks remotely sensing, the better the plant will grow
Cotton fields 7 and 8 in the picture below are growing significantly better than the other plots
(Changes in NDVI in Yuli County, Xinjiang Figure: "Yunzhi" Digital Agriculture Platform)
How to interpret the corresponding geographic information from satellite data is a difficult problem that many scholars around the world are tackling, which often requires the combination of theoretical calculations and empirical formulas.
▲Caption: Through remote sensing satellites
Changes in vegetation cover are visible
(Badain Jaran Desert Map: Picture Worm Creativity)
This planet and the life on it are so rich and colorful that from outside the earth, only its vague shadow can be seen, and it must go out of it and enter it again in order to gradually piece together the whole picture.
Every early spring, people in the north who are troubled by sandstorms will always ask: why are there still sandstorms after so many years of greening? To a large extent, this comes down to land degradation in Outer Mongolia.
▲Caption: This is how the land has been degraded
Sandstorms are no surprise
(Degraded steppe in Mongolia Photo: Yitu.com)
Disasters know no borders and do not stop at national borders. Whether it is the Eurasian steppe or the earth, there is only one.
In 1968, the astronauts on Apollo 8 took a famous "earth-rising" photo in space, and the creatures who had lived on Earth for hundreds of millions of years saw the whole picture of their home for the first time.
▲Caption: This bright and fragile planet
It is the common home of human civilization
(Earthrise)
With the exception of astronauts on the space station, remote sensing satellites are the only means by which we can see the entire planet. Grasslands, forests, rivers, lakes, and the land are all wonderful.
When we see the human home in its entirety, we want to take care of it even more. This is perhaps the greatest significance of remote sensing technology in addition to scientific research.
▲Caption: Overlooking the devastated Aral Sea from space
The shocking desertification of the land is clearly visible
(The Aral Sea is disappearing, Photo: Yitu.com)
In comparison, the worst grassland in China, Mongolia and Kazakhstan is Mongolia
How Mongolia is on the brink of environmental collapse can be found in this video
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Mongolia's Environmental Collapse Report: Squeezing Dry from Top to Bottom [Earth Knowledge Bureau]
*The content of this article is provided by the author and does not necessarily represent the position of the Earth Knowledge Bureau
Cover: Yitu.com
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