Dryland nature-based solutions emerge as climate lifeline for semi-arid Windhoek

Windhoek, the capital of Namibia, sits more than 1,600 meters above sea level on the eastern edge of the Khomas Highland, in one of the most water-stressed urban environments in southern Africa. The city receives an average of roughly 370 millimeters of rain per year, almost all of it concentrated in a short summer wet season, and potential evaporation far exceeds rainfall across most months. For decades, this semi-arid setting has made Windhoek a global reference point for unconventional urban water management, from its pioneering direct potable reuse scheme to aggressive demand management. A new study published in npj Urban Sustainability turns the city’s dryland conditions into a lens for examining nature-based solutions, asking what role vegetation, soils, green infrastructure, and restored ecosystems can realistically play in helping a fast-growing African city adapt to a hotter, more variable climate.

Nature-based solutions have moved rapidly up the policy agenda over the past decade. Defined broadly as actions that protect, sustainably manage, or restore natural or modified ecosystems while simultaneously delivering human well-being and biodiversity benefits, they encompass everything from urban forests and rain gardens to wetland restoration and catchment protection. Most of the scientific evidence behind these approaches, however, comes from temperate, humid cities in Europe and North America. Researchers have repeatedly warned that this evidence base cannot simply be transplanted to drylands, where water is the dominant constraint on ecological function and where green infrastructure that works in Berlin or Portland may fail, or even backfire, in Windhoek.

The new research addresses this gap by systematically assembling evidence and insights on dryland nature-based solutions in the specific context of semi-arid Windhoek. The study frames the city as a critical test case: it is a national capital with substantial technical capacity and a long institutional memory of water crisis management, yet it operates under hydrological conditions that stress every assumption of conventional green urbanism. By focusing the analysis on what is actually known, rather than what is assumed, the authors aim to give planners and policymakers a realistic account of where nature-based approaches can deliver climate adaptation benefits and where their limits lie.

The technical logic of the assessment rests on the water balance. In a semi-arid city, every hectare of vegetation consumes water through evapotranspiration, and every liter allocated to greening is a liter not available for households, industry, or the treated wastewater on which Windhoek heavily depends. This means that the desirability of any nature-based intervention depends on its water source and its return on that investment. Interventions that harvest rainwater, infiltrate stormwater into soils, or make use of treated effluent can be water-positive; interventions that rely on potable supplies to maintain ornamental greenery can erode the very resilience they are meant to build. The study situates dryland nature-based solutions squarely within this accounting framework, treating water sourcing as the first-order design question rather than an afterthought.

Windhoek’s own history supplies much of the empirical texture. The city has endured repeated droughts, including the severe regional drought of 2019 that forced drastic supply cuts and left reservoirs at historic lows. Its response arsenal has included some of the world’s most advanced engineered systems: since the late 1960s, Windhoek has practiced direct potable reuse of treated municipal wastewater, and its integrated water demand management has kept per-capita consumption far below that of many comparable cities. Yet these achievements are engineered rather than ecological, and the new study asks whether the city’s green assets, its river corridors, urban trees, open savanna remnants, and informal green spaces, have been integrated into adaptation planning with the same rigor as its pipes and reclamation plants.

A central thread of the analysis is the distinction between different functional classes of nature-based solutions and their suitability to dryland conditions. Vegetated drainage lines and rehabilitated seasonal river channels, for instance, can slow and infiltrate episodic storm flows, reducing flood damage during intense summer storms while recharging soils and shallow groundwater. Xeriscaping and the use of drought-adapted indigenous species can deliver shade, cooling, and amenity at a fraction of the water cost of exotic turf and temperate ornamentals. Protecting remnant thornveld and rocky hillside habitats within the urban fabric can sustain biodiversity and cultural values without ongoing irrigation. Each of these options reflects the study’s core insight that in drylands, nature-based solutions succeed when they are designed to work with scarcity rather than against it.

The cooling question receives particular attention, because urban heat is among the most direct climate threats to dryland cities. Windhoek already experiences hot summers, and climate projections for central Namibia indicate more frequent and intense heat extremes, which bear hardest on low-income neighborhoods with limited access to shade and cooling. Trees and vegetated areas cool their surroundings through shade and evapotranspiration, but in a semi-arid context the cooling benefit must be weighed against the water consumed. The evidence assembled in the study points toward targeted, water-efficient greening, priority shade trees along pedestrian routes, canopy in schools and clinics, and greenery irrigated with treated effluent, as the configurations most likely to deliver heat protection without compromising water security.

Governance emerges as a second major theme. The study emphasizes that nature-based solutions are not merely planting projects; they are long-term institutional commitments that require land tenure clarity, maintenance budgets, cross-departmental coordination, and community stewardship. In Windhoek, as in many Southern African cities, the urban landscape is deeply unequal, with leafy former suburbs adjoining dense informal settlements where green space is scarce and heat exposure is high. The study argues that climate adaptation through nature-based approaches will be judged not only by hectares greened or liters saved, but by whether the benefits reach the households most exposed to drought, heat, and flood risk. Community-based management, aligned with existing municipal programs, is identified as a practical pathway for sustaining interventions in contexts where municipal maintenance capacity is stretched.

Equally important is the study’s treatment of evidence quality itself. The authors stress that much of the global literature on urban nature-based solutions reports outcomes from mesic environments, and that dryland-specific monitoring data, on infiltration rates, water use, survival of planted vegetation, thermal performance, and social benefits, remain thin, particularly for African cities. Windhoek’s long records of hydrology, water demand, and urban development offer an unusually rich foundation for closing this gap, and the study positions the city as a living laboratory in which carefully monitored pilots could generate the quantitative evidence that dryland urban planners elsewhere currently lack. The recommendation is not to wait for perfect data, but to embed measurement into every intervention from the outset, so that each rain garden, rehabilitated channel, and shade corridor doubles as a research site.

The broader significance of the work extends well beyond Namibia. Hundreds of millions of people now live in dryland cities, from the Sahel to the Middle East to the American Southwest, and that population is growing faster than the global average even as climate change intensifies aridity. For these cities, the Windhoek case suggests that nature-based solutions must be reframed: less about lush greenery and more about strategic, water-aware deployment of dryland ecosystems to buffer floods, heat, and livelihood shocks. The study’s message to the international research and policy community is that semi-arid African cities are not peripheral test beds for ideas developed elsewhere, but front-line innovators whose constraints are producing insights the rest of a drying world will increasingly need. In Windhoek, the future of urban climate adaptation is being written with very little water, and that, the authors argue, is precisely what makes it worth watching.

Subject of Research: Dryland nature-based solutions for climate adaptation in semi-arid Windhoek, Namibia

Article Title: Evidence and insights on dryland nature-based solutions for climate adaptation in semi-arid Windhoek, Namibia

Article References: Evidence and insights on dryland nature-based solutions for climate adaptation in semi-arid Windhoek, Namibia. (n.d.). https://doi.org/10.1038/s42949-026-00468-0

Image Credits: AI Generated

DOI: 10.1038/s42949-026-00468-0

Keywords: nature-based solutions, drylands, climate adaptation, Windhoek, Namibia, semi-arid cities, urban sustainability, water security, urban heat, urban greening, water demand management, drought resilience