290 million new city dwellers benefit China’s climate balance

Land Use / Covering Systems and MODIS Carbon Density Changes in China. Credit: DOI: 10.1038 / s41893-021-00843-y

Contrary to popular belief, large-scale migration from rural areas to cities in China has been shown to have a positive impact on China’s carbon storage. Urbanization can also play a role in achieving climate neutrality. This is the conclusion of researchers at the University of Copenhagen based on the analysis of vast amounts of satellite data.

Urbanization is an explosive trend in most parts of the globe. Nowhere has more than 290 million people migrated to cities in the last three decades from rural areas as large as China.

Urbanization is generally perceived as a trend associated with increased greenhouse gas emissions. It is envisioned that when carbon-isolating forests are logged to make room for urban growth, the carbon stored there will be released and CO will be generated.2 Emissions will increase.

However, with the help of remote sensing technology that maps natural resources using satellite observations, researchers at the University of Copenhagen are now rejecting that assumption. On the contrary, their research shows that urbanization in China over the last two decades has led to an increase in both biomass and carbon storage. Rural areas And a recently developed city.The survey results were published in the journal Nature sustainability..

“Nevertheless Urban growth To blame the loss of carbon in the first half of the period, the Green Policy Initiative will make up for the loss and lead to an overall balance effect. Indeed, a small surplus in the climate account has been achieved, “explains PhD student Xiaoxin Zhang, lead author of research in the Faculty of Earth Sciences and Nature Management at the University of Copenhagen.

From 2002 to 2010 in China Urban area We experienced carbon loss from 20 million tonnes of above-ground biomass. However, the total carbon balance from 2002 to 2019 ended up with an increase of 30 million tonnes of carbon in urban areas. China’s total ground carbon storage has increased by 290 million tonnes annually.

From a large area to a small area

China’s tree-planting strategy has produced billions of new trees in recent decades, thereby playing an important role in the country’s carbon balance. But new forest plantations do not explain everything.

“When people move to densely populated urban areas, they leave vast lands behind. This relieves pressure. Natural vegetation Allows new vegetation to absorb carbon. At the same time, the declining population from rural areas has provided more space for planting new trees in the countryside, “said Xiaowei Tong, a postdoctoral fellow in the Earth Sciences and Natural Resources Management Department at UCPH.

Growth of parks and green spaces

Tree coverings have also grown in cities over the last decade. The Chinese government’s ecological civilization policy secures a certain percentage of city parks, trees, rooftop greenery, vertical gardens, etc.

“There may be a lot of criticism of China, but when it comes to incorporating green space into urban planning, China is very advanced. The recent increase in urban carbon absorption sources is a positive city. Very likely to be the result of a greening policy .. This supplements CO2 Trees and plants are released when they are logged for urban development, “says Professor Rasmus Fenholt of the Department of Earth Sciences and Natural Resources Management.

He adds: “It even suggests that urbanization can be an integral part of the recipe for reducing CO.2 Emissions if urban development is designed to be sufficiently environmentally friendly. “

Minimize invasion of forests and farmlands

Analysis also shows that the growing pain of the city has little impact on the country’s forests. Only 6 percent of urban expansion was brought about at the expense of forest areas.Instead, new developments were mostly replaced Agricultural land (81%) and grassland (10%)-Types of vegetation with low carbon storage potential compared to tree coverings.

Despite the city’s largest invasion of farmland, China’s farmland has shrunk by only 3.8% during this period. In most cases, this is probably due to increased agriculture and increased food imports.

“There is talk of urbanization destroying vast vegetation and replacing greens with concrete and asphalt, which shows that this is not the case in China,” said Martin Brandt, assistant professor of the Earth Sciences and Natural Resources Management Department. Says. ..

Tree planting alone is not enough

If China is to reach its climate-neutral goal by 2060, researchers point out that tree planting alone is not enough.

“There is a limit to how much and how long a tree can absorb CO.2.. At some point, mature forests completely stop carbon recovery. Therefore, if China wants to be climate-neutral, planting more trees is not enough. For this reason, it is important to significantly reduce emissions from fossil fuels. Nonetheless, in this study we observed what is called a green transition kickstart, “explains Professor Fenholt.

“Overall, data from China show that once appropriate conditions are established, cities can be expanded and carbon capture increased at the same time. This is a low-income country that wants to improve its climate footprint and overall. Environmental conditions that can serve as an inspiration for, “says Martin Brandt.

Researchers emphasize that the findings are composed of key components, but not the entire equation of China’s climate footprint in urban areas. In particular, the footprint of food imports is not taken into account.

A green backyard helps to increase the resilience of the city’s climate

For more information:
Xiaoxin Zhang et al, a large but temporary carbon sink due to urbanization and rural depopulation in China, Nature sustainability (2022). DOI: 10.1038 / s41893-021-00843-y

Quote: 290 million new urban dwellers are benefiting China’s climate balance (February 23, 2022).

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290 million new city dwellers benefit China’s climate balance

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