Urbanization is usually judged by what is built, but it should also be evaluated according to what it hollows out. Around the world, increasing numbers of people are moving to cities — 67% of the global population is projected to live in urban areas by 2050¹. But this trend is about more than people relocating.

The rural regions that migrants leave behind are being steadily dismantled. Globally, up to 400 million hectares of land have been abandoned since the 1950s² and up to half of the world’s rangelands (large expanses used as grazing land for livestock) are considered degraded³. Meanwhile, growing urban demand for food, water and biomass is intensifying the extraction of resources beyond city boundaries. The effects of these pressures are already evident in Europe’s emptying interiors, East Asia’s vanishing towns and Latin America’s swelling informal settlements.

How buildings and cities can be aligned with life

These diverse cases expose a common policy oversight: a tendency to treat urban greening and nature-based solutions as an environmental cure-all. But cities depend on their hinterlands for survival — these areas provide food, deliver water and sequester carbon. Yet, the creation of urban green space doesn’t prevent working countryside from losing its human stewards, its fertile topsoil and the capacity to sustain ecosystem services.

Addressing this crisis requires managing urban and rural domains as a single entity. Here, we outline an approach that combines geospatial monitoring, landscape engineering and watershed planning to optimize ecological productivity and livelihoods in the countryside.

One-way flow of resources

Rural decline is driven by three kinds of flow: demographic, land and ecosystem. Demographic flows begin when working-age populations migrate to cities to find better-paid jobs and more affluent lifestyles. With fewer workers left in rural areas, infrastructure and services diminish. Many remaining families are then forced to relocate, eroding both the tax base and local memory. Land flows refer to changes in land use driven by urban demand, whereas ecosystem flows describe transfers of water, biomass and ecosystem services from rural areas to cities.

Globally, thousands of small towns and villages face severe declines in population (see ‘Growing cities, lost countryside’). In Spain alone, some 4,000 of around 8,000 municipalities have fewer than 13 residents per square kilometre⁴; the Iberian Highlands in the centre and east of the country have roughly two residents per square kilometre (see go.nature.com/4agrer).

Meanwhile, a 2024 report classed 744 of 1,729 Japanese municipalities as being at risk of severe population decline⁵ — defined as a fall of at least 50% in the number of women aged 20–39 between 2020 and 2050. Nanmoku in Gunma Prefecture illustrates this pattern: its population fell by 73% between 1980 and 2020 (see go.nature.com/4y5lpnc); by 2024, roughly two-thirds of its remaining residents were aged 65 or older.

Long-term rural-to-urban migration has also reshaped settlement patterns in Brazil. In 2022, 16.4 million people lived in informal favelas and other urban communities, accounting for 8.1% of the national population⁶. In neighbouring Colombia, research has shown that poverty and instability are associated with a heightened risk of rural depopulation⁷.

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Metropolitan centres don’t just take in people; they draw on land, water and biomass from far beyond their administrative borders, in a one-way subsidy from the countryside to the city⁸. Beijing’s urban areas, for example, receive nearly 80% of their water through a transfer system from the Danjiangkou Reservoir, more than 1,000 kilometres away. Landscapes surrounding cities are often treated as disposable hinterlands, and fragile ecosystems are turned to crop production. Between 2000 and 2018, almost 90% of global deforestation was linked to agricultural expansion⁹.

This disconnect between where resources are produced and where they are consumed precipitates a ‘rural decline syndrome’, triggering the collapse of demographic, economic and environmental capital across rural communities worldwide.

Why policy interventions fail

Conventional policies and initiatives such as green roofs fall short because they treat isolated symptoms rather than addressing the interconnected nature of these rural decline flows. Urban greening strategies can also contribute to gentrification, which sees richer people inhabit leafier areas, widening socioeconomic and health disparities¹⁰.

Greener cities: a necessity or a luxury?

Similarly, government subsidies to rural regions function only as temporary palliatives. The European Union’s Common Agricultural Policy has a budget equivalent to roughly €55 billion a year, but the support it provides remains highly concentrated. Between 2014 and 2020, 20% of beneficiaries received 80% of direct payments¹¹.

Targeted investments in infrastructure also remain insufficient when deployed in administrative silos. In Japan, increased funding for rural roads and broadband access has failed to curb demographic collapse in its municipalities. Without integrating infrastructure with local land management and ecological restoration strategies, such networks simply accelerate the extraction and flow of rural assets towards metropolitan hubs.

How engineering can help

We propose a framework for considering flows of people, land and ecosystem services that merges Earth-system science, geospatial modelling and landscape engineering. We call it Geo-STEP (Geographical Science–Technology–Engineering–Practice).

The components of Geo-STEP include a biophysical assessment of the territory; a landscape-wide plan for managing land, water, carbon and jobs; and a programme of scientific monitoring and engineering interventions to optimize both ecological productivity and human livelihoods.

The Gully Land Consolidation project around the city of Yan’an on China’s Loess Plateau illustrates these principles. The programme, which started in 2011, aims to restore more than 2,600 square kilometres of agricultural land across the dry, eroded plateau by consolidating more than 2,000 gullies and introducing a regional land- and resource-management plan¹².

The loess slopes, made from wind-blown silt, were susceptible to erosion by rainwater. Run-off during storms was enlarging the gullies, causing fertile topsoil and other sediments to be carried downstream. To remedy this, workers excavated soil from the hill-slopes and compacted it inside the gullies. They planted the cut slopes and built drainage channels and dams to control water flow, managed through a region-wide watershed plan.

Scientists also used satellite remote sensing, soil surveys and hydrological models to inform the engineering designs and tracked outcomes from field stations. Levelling the gullies enhanced the storage of organic carbon in the soil through the deposition of uphill sediments and accumulation from plants and their roots.

The newly created cropland supports local agricultural production, strengthening food security and securing rural livelihoods. Stabilized slopes, drainage structures and dams help to reduce run-off and sediment delivery to downstream channels.

An adaptive approach

Such coherent methodologies can be adapted for diverse contexts around the world, using different technologies, funding mechanisms and forms of community engagement.

In the East African Highlands, for example, watershed management programmes could scale up traditional hillside terracing. Community-based land-governance systems could be linked with satellite-driven hydrological tracking to secure upstream water sources and prevent silt from building up downstream.