Can botanical gardens save cities from themselves?

What if the most cost-effective public health intervention, climate adaptation tool, and biodiversity conservation strategy for cities were all the same thing - and it had been around for centuries?

A commentary published in Biological Diversity by Xiangying Wen and Hai Ren of the South China Botanical Garden (Chinese Academy of Sciences) and Timothy John Entwisle of Royal Botanic Gardens Victoria makes a case that botanical gardens are not ornamental amenities but critical infrastructure for urban sustainability. The argument arrives as 66% of China's population and over 80% of the population in developed nations now lives in cities - environments increasingly defined by heat islands, air pollution, biodiversity loss, and a growing disconnect between humans and the natural world.

Six functions, one institution

The authors identify six core functions that modern botanical gardens deliver: conservation, scientific research, public education, resource utilization, recreation, and garden display. The conservation role alone is substantial - botanical gardens worldwide collectively maintain roughly 30% of the world's wild plant species in ex situ collections, preserving genetic material outside natural habitats as insurance against extinction.

But the commentary pushes beyond the traditional conservation framing. Botanical gardens, the authors argue, function as urban ecological infrastructure. They mitigate heat islands through canopy cover and evapotranspiration. They filter air pollutants. Their research programs inform the development of climate-adaptive urban systems - identifying drought-resistant species for green roofs, selecting plants for stormwater management systems, and building the knowledge base for low-maintenance, high-biodiversity urban habitats.

Royal Botanic Gardens Victoria's Landscape Succession Strategy, launched in 2016, is cited as an example. That program, which plans for how the garden's living collections will need to change as Melbourne's climate shifts, helped catalyze an international Climate Change Alliance among botanical institutions.

Green space that measurably reduces anxiety

The mental health dimension is where the commentary gets most specific. The authors outline seven mechanisms through which botanical gardens improve quality of life: satisfying curiosity about plants, improving leisure quality, contributing to local economic activity, building scientific literacy, reducing stress, addressing eco-anxiety, and delivering therapeutic horticulture programs.

They cite research showing that greater biodiversity in green spaces correlates with stronger psychological benefits. A park with 200 plant species delivers more mental health value than a park with 20 - and botanical gardens, by definition, maximize species diversity. The authors frame this as a low-cost, high-yield public health intervention, particularly relevant as urban mental health challenges intensify globally.

Three stages of city-garden integration

The commentary traces an evolution in how botanical gardens relate to their host cities. The first stage - "botanical gardens in cities" - treats the garden as a distinct institution within the urban fabric, valuable but separate. The second stage - "cities in botanical gardens" - describes deeper integration, where botanical garden principles influence urban planning, streetscaping, and infrastructure design. The third stage - "cities in nature" - envisions cities designed around ecological principles from the ground up, with botanical gardens as embedded nodes in a broader urban ecological network.

The authors align this trajectory with the Kunming-Montreal Global Biodiversity Framework and the Global Strategy for Plant Conservation (2023-2030). They propose five action areas: strengthening conservation capabilities through ex situ programs and ecological restoration research; promoting collaborative innovation between gardens and urban planners; enhancing public engagement and education; aligning garden programs with the UN Sustainable Development Goals (particularly Goal 11, Sustainable Cities and Communities); and removing access barriers to ensure gardens serve all communities, including vulnerable populations.

Green prescriptions and spatial belonging

Several of the practical examples the authors cite are already operating. Some gardens run "Plant Adoption" programs targeting vulnerable groups. Others have centered immigrant and low-income communities in planning processes, deliberately designing spaces and programs that foster what the authors call "spatial belonging" - the feeling of being welcome in and connected to a place.

The concept of "green prescriptions" - where medical professionals direct patients to therapeutic horticulture programs at botanical gardens - represents another integration point. Evidence for horticultural therapy's effects on conditions ranging from depression to post-traumatic stress disorder has been building for years, and several gardens now partner with healthcare institutions to offer structured programs.

What the commentary does not address

The piece is a commentary, not an empirical study, and it reads more as advocacy than analysis. The authors make broad claims about botanical gardens' contributions to urban sustainability without systematically comparing their cost-effectiveness against alternative interventions - urban forestry programs, constructed wetlands, engineered green infrastructure, or simple park expansion.

The 30% figure for ex situ plant conservation is global and aggregate. How well those collections represent the most threatened species, how genetically viable the conserved populations are, and whether ex situ conservation at botanical gardens translates into successful reintroduction to wild habitats are questions the commentary does not examine in depth.

Funding and institutional sustainability also go largely unaddressed. Many botanical gardens, particularly in developing nations, face chronic underfunding. Arguing that gardens should take on expanded roles in urban climate adaptation, public health, and social inclusion without addressing how those expanded mandates will be resourced risks setting expectations that institutions cannot meet.

The mental health claims, while supported by a growing body of research, rely heavily on correlational studies. Establishing that botanical garden visits cause mental health improvements - rather than that healthier, wealthier people visit gardens more often - requires controlled intervention studies that remain relatively rare in the literature.

Still, the core argument is sound: botanical gardens offer a proven, multifunctional model for delivering ecological services, education, conservation, and well-being benefits in urban environments. Whether cities choose to invest in them as infrastructure - rather than treating them as pleasant extras - is a policy decision, not a scientific one.