Evaluating Carbon Storage Responses to Land Use Change under Multi-Scenario Simulations: A GMOP–PLUS–InVEST Coupled Framework for Border Cities

The land beneath our feet is not just dirt; it is a vast, living vault that holds carbon, the element at the heart of our climate. When forests grow, they pull carbon from the air and lock it away in their trunks and roots. When we pave over fields or cut down trees, that stored carbon often escapes back into the atmosphere, warming the planet. This balance is delicate, and it shifts constantly as cities expand and nature responds. For decades, scientists have tried to understand how human decisions about land use—where we build, where we farm, and where we let nature reclaim the ground—alter this global carbon vault. The challenge lies in predicting the future: if a city grows in one direction, does it destroy more carbon than it saves in another? To answer this, researchers must look at the complex dance between economic needs, government policies, and the physical landscape, trying to find a path where both people and the planet can thrive.

In the border city of Dandong, China, a team of researchers has taken a deep dive into this question, using a sophisticated digital laboratory to simulate how the land might change over the next few years. Dandong sits at a critical junction where the mountains meet the sea, a place where rapid urbanization clashes with the urgent need to protect the environment. The scientists wanted to know how different choices for the city's future would affect its ability to store carbon. They did not just guess; they built a computer model that combined three powerful tools. First, they used a system to optimize the city's land structure, weighing the value of forests against the value of farms and factories. Next, they used a simulation engine to map out exactly where new buildings or new forests would likely appear on the ground. Finally, they calculated how much carbon each of these land types would hold. By running these simulations under four different future scenarios, they created a clear picture of the trade-offs facing the region.

The history of Dandong's land use over the last two decades offers a striking story of loss and recovery. Between 2000 and 2020, the city's total carbon storage dipped slightly before climbing back up, a "decline-then-increase" pattern that mirrors the region's shifting priorities. In the early years, the rapid expansion of construction land ate into farmland, causing a net loss of carbon. However, as the decade progressed, a massive push to turn farmland back into forest, driven by national ecological programs, began to pay off. The forests grew so much that they more than made up for the lost farmland, resulting in a net gain of over 5.2 million tons of carbon stored by 2020. The researchers found that this recovery was not uniform; the northern mountainous areas became strongholds of carbon storage as trees reclaimed the slopes, while the southern coastal plains, where industry and housing expanded, saw their carbon levels drop.

Looking ahead to the year 2030, the simulations revealed that the city's future carbon storage depends entirely on the path chosen by its planners. If the city follows a path of pure economic development, prioritizing factories and housing, the carbon gains will be minimal, rising by less than one percent. In this scenario, the expansion of construction land would continue to eat away at the carbon-rich soil of the farmlands. Conversely, if the city prioritizes ecological protection, converting vast swathes of farmland back into forests and wetlands, the carbon storage could jump by more than six percent. This "ecological protection" path would create a massive carbon sink, but it comes with a steep price: a significant reduction in the area available for farming. The researchers identified a middle ground, a "comprehensive development" scenario, which balances the two. In this simulation, the city allows for moderate growth in construction land while still protecting enough forest to increase total carbon storage by nearly six percent, proving that economic growth and environmental health do not have to be enemies, provided the land is managed with care.

The study also peeled back the layers to understand why carbon storage is distributed the way it is across the landscape. The researchers discovered that the most powerful drivers are not just human choices, but the physical shape of the land itself. The steepness of the slopes and the height of the terrain play a dominant role in where forests grow and where cities can expand. However, the most surprising finding was how these physical factors interact with the health of the vegetation. The combination of steep slopes and healthy, green vegetation creates a powerful synergy, making those areas the most effective places for storing carbon. This suggests that planting trees on steep, degraded hillsides is not just a good idea for preventing erosion; it is a highly efficient strategy for capturing carbon. The data showed that the influence of these natural factors has grown stronger over time, overtaking economic factors as the primary shaper of the carbon landscape.

Ultimately, the work in Dandong offers a blueprint for other border cities and rapidly developing regions facing similar dilemmas. The researchers concluded that a "one-size-fits-all" approach to land management will fail. Instead, they advocate for a strategy of zoning, where different parts of the city are treated according to their natural strengths. The northern mountains, with their steep slopes, should be prioritized for forest restoration to maximize carbon capture, while the southern coastal plains should have strict limits on how much farmland can be converted into industrial zones. By aligning human development with the natural contours of the land, cities can secure their economic future without sacrificing the climate stability that depends on the soil and trees beneath them. The study confirms that with the right mix of policy and planning, it is possible to grow a city while simultaneously growing its capacity to heal the planet.