Simulation Study for Constructing Ecological Security Pattern: A Couple d InVEST-PLUS Model Approach

In the arid and semi-arid regions of northwest China, the land is a fragile balance between human needs and nature's limits. Here, the ground is often sandy, water is scarce, and the ecosystem is easily disrupted by climate change and human activity. To keep this environment from collapsing, scientists look for an "ecological security pattern." Think of this not as a single fence or wall, but as a living map of the most vital pieces of land. This map identifies three key things: the "sources," which are the healthiest, most protected patches of nature; the "corridors," which are the pathways that allow wildlife and natural processes to move between these patches; and the "nodes," which are the critical junctions where these paths meet. Without these connections, nature becomes fragmented, and the region's ability to provide clean water, stable soil, and a safe habitat for life begins to fail. The challenge for researchers is that the land is never static; it changes every year as cities grow, farms expand, or forests are planted. A plan that works today might fail tomorrow if it does not account for how the land will look in the future.

To solve this puzzle for the Mu Us Sandy Land, a vast desert region in northern China that serves as a critical ecological barrier, a team of researchers from Yan'an University and Chang'an University developed a new way to look ahead. Instead of just studying the land as it is right now, they built a computer simulation to predict how the landscape would change by the year 2030 under different conditions. They imagined three possible futures: one where development happens naturally without much interference, one where the economy is the top priority, and one where protecting the environment is the main goal. Using a sophisticated computer model called PLUS, they simulated how different types of land—such as farmland, forests, grasslands, and construction sites—would shift and spread across the region in each of these scenarios. This allowed them to see not just where the land is today, but where it is likely to be in the near future.

Once they had these future maps, the team needed to find the most important spots to protect. They realized that looking at just one factor, like how much water a forest produces, was not enough. They also needed to consider how vulnerable the underground water was to pollution and drying up. So, they combined two different assessments. First, they used a tool called InVEST to measure how well the land provided essential services like cleaning water, storing carbon, and protecting habitats. Second, they used an improved version of a groundwater vulnerability model to see which areas were most at risk from human activity and pollution. By layering these two maps together, they could pinpoint the true "ecological sources"—the areas that were both highly valuable for nature and safe from groundwater risks. They found that under a natural development scenario, there would be five main source areas, covering about 13 percent of the region, mostly located along the western, eastern, and northern edges.

With the sources identified, the researchers then mapped out how nature could move between them. They created a "resistance surface," which is essentially a map showing how difficult it is for ecological processes to travel across different parts of the landscape. For example, a busy city or a steep slope acts as a high-resistance barrier, while a grassy plain is easy to cross. Using a method based on how electricity flows through a circuit, they traced the most efficient paths between the sources. This analysis revealed six major ecological corridors, stretching a total of 314 kilometers, which act as the arteries for the region's ecosystem. They also identified 120 specific "pinch points," which are narrow bottlenecks where the flow of nature is most easily blocked, and 605 square kilometers of "barrier areas" that need to be cleared or managed to keep the system working.

The study's findings highlight that the future of this region depends heavily on the choices made today. In the scenario where economic development is prioritized, the amount of land used for construction would remain the highest, but this would come at the cost of losing more farmland and reducing the area of grasslands. In contrast, the scenario focused on ecological protection showed the largest increase in grassland and the smallest loss of forest, suggesting that policy decisions can significantly shape the landscape. The researchers found that under a natural development path, the most significant change would be a sharp drop in construction land, with much of it reverting to grassland. However, they also noted that simply protecting what exists is not enough; the system must be dynamic. The study suggests that to ensure the long-term health of the Yellow River Basin and prevent further desertification, managers must balance economic needs with strict protection of these identified sources. They recommend strengthening the corridors to connect the isolated patches of nature and optimizing the pinch points to ensure that energy and species can flow freely. By using these simulations to guide their actions, planners can move beyond static protection and create a resilient network that adapts to a changing world.