The study area could hardly be more instructive. Sintra, covering approximately 319 square kilometres in the Lisbon Metropolitan Area and home to around 385,000 people, is a municipality of stark internal contrasts. Its north-western quadrant is dominated by the Sintra–Cascais Natural Park, a protected mountainous landscape of roughly 14,590 hectares of forested terrain and cultural landmarks. Its eastern sector, by contrast, is a dense band of suburban development—the parishes of Algueirão-Mem Martins, Agualva e Mira-Sintra, Massamá e Monte Abraão, and Rio de Mouro—where high population densities coincide with a relative scarcity of green spaces larger than one hectare. The park’s rugged topography, with elevations reaching 514 metres, and its infrastructure geared toward nature tourism mean that much of it lies outside the routine activity spaces of lowland residents, particularly those without cars, training, or mobility. On paper, Sintra looks abundantly green; functionally, its eastern neighbourhoods are “green deserts.”

To measure this discrepancy rigorously, the team first built an inventory of leisure green spaces from the official municipal cadastre, retaining only sites that either offered functional amenities for active recreation—playgrounds, sports courts, or similar facilities—or met a minimum size threshold of one hectare, in line with World Health Organization recommendations and the United Kingdom’s Accessible Greenspace Standards. Crucially, the researchers then abandoned the conventional Euclidean buffer approach, in which access is judged by straight-line distance, in favour of network-based service area analysis performed in ArcGIS Pro Network Analyst. Accessibility was computed along the actual topological structure of the pedestrian street network, using walking time as the impedance attribute derived from segment lengths and an assumed average pedestrian speed of 4.5 kilometres per hour. Service areas were generated at three cumulative travel-time cutoffs—0–5, 5–10, and 10–15 minutes—producing pedestrian isochrones that capture the real barriers imposed by street connectivity, high-speed transit corridors, and Sintra’s fragmented road system.

The results are sobering. Approximately 183,000 residents live within a five-minute walk of a qualifying leisure green space, concentrated in well-served central areas such as Queluz, Agualva-Cacém, and Algueirão-Mem Martins. Another 80,000 fall within the 5-to-10-minute band, and only about 36,700 within the 10-to-15-minute interval. Beyond that threshold, roughly 82,000 inhabitants—about 21 percent of the municipal population—remain entirely outside the effective service area of any qualifying green space, a deficit that falls disproportionately on high-density eastern neighbourhoods including Tapada das Mercês, Mem Martins, and parts of Agualva-Cacém. By intersecting the accessibility isochrones with 2021 census population density data, classified into four categories using the Jenks natural breaks method, the team produced a sixteen-class spatial typology that exposes the sharpest mismatches: areas combining medium-to-high population density with low or null walkable access. Population counts were apportioned among statistical subsections intersected by service-area rings using areal weighting, with subsections whose overlap fell below 50 percent excluded to avoid spurious inflation—a conservative reconciliation designed to keep estimates honest and non-duplicated.

With the deficit map in hand, the researchers turned to identifying where new green spaces should go. Five criteria were selected and harmonised onto a common 0-to-100 suitability scale after projecting all layers to the ETRS89/Portugal TM06 coordinate system and rasterising at a uniform one-metre resolution. The criteria were proximity to existing leisure green spaces, buffer zones around highly populated areas, land-use suitability based on the 2018 Portuguese land cover map, proximity to schools as a proxy for the social dimension of access, and the regulatory footprint of the Sintra–Cascais Natural Park. Notably, land ownership was deliberately not used as an exclusion filter: at the strategic screening stage, the model aims to identify where new green space would yield the greatest gains, leaving tenure questions—acquisition, negotiation, or regulatory instruments—to a later adaptive-planning phase.

To weight these criteria objectively, the team applied the Analytic Hierarchy Process, the pairwise comparison method introduced by Thomas Saaty. Judgements were elicited from a focus group of eight participants, including municipal planning officers from the Câmara Municipal de Sintra and researchers specialised in urban ecology and spatial analysis, with individual matrices aggregated via the geometric mean. The resulting weights reveal a clear value orientation: demographic pressure, expressed as buffers around highly populated areas, received the highest weight at 29 percent, followed closely by the pedestrian accessibility gradient at 25 percent. Land-use suitability took 20 percent, proximity to schools 16 percent, and the Natural Park criterion just 10 percent—reflecting its regulatory rather than demand-driven character. Internal consistency was confirmed with a Consistency Ratio of 0.04, comfortably below the accepted 0.10 threshold, and a one-at-a-time sensitivity analysis perturbing each weight by ±10 percent produced only marginal changes and did not alter the ranking of priority sites, indicating robust model outputs.

The weighted overlay produced a composite suitability index normalised to 0–100 percent and classified into five equal-interval categories. Only areas exceeding 80 percent suitability were retained, filtered by a minimum size of one hectare and dissolved to eliminate fragmentation, yielding 96 candidate areas totalling 967.22 hectares with a mean size of 9.6 hectares. Built-up land accounted for only 5.74 hectares—about 0.6 percent of the selected area—demonstrating that the model overwhelmingly favoured non-urbanised land such as forests, agricultural plots, and abandoned shrubland, thereby minimising conflicts with existing residential uses. No qualifying sites emerged in the western parishes of São João das Lampas e Terrugem, Colares, or Almargem do Bispo, while the highest concentration appeared precisely where demographic pressure and accessibility deficits converge: Algueirão–Mem Martins and Agualva–Mira Sintra. From these candidates, the five largest continuous parcels were selected as priority intervention areas, ranging from 14.1 to 27 hectares, located primarily in Tapada das Mercês, Vale Mourão, and Chão de Meninos.

Network-based estimates suggest that establishing these five parks would improve walkable access to leisure green spaces for approximately 68,200 residents—a de-duplicated figure derived from a single combined service-area solve, since the sites’ catchments overlap spatially. The analysis also surfaced a cautionary tale about data latency. Site 4, Vale Mourão II, was scored as shrubland based on the 2018 land cover dataset, but between 2018 and 2026 a fully sealed open-air car park was built over part of the parcel. Because the conversion postdates the land cover input, the impervious surface is invisible to the model, and the site is rated more suitable than its current physical state warrants. The researchers flag this as an exemplar of the temporal-latency limitation of static land cover data, while noting that the low-intensity built use is reversible, so the parcel retains genuine potential for green-space conversion or partial renaturalisation—a form of adaptive urbanism in which even parking infrastructure can be reclaimed for nature.

Beyond its local findings, the study makes a broader methodological argument: nominal proximity is a poor proxy for experienced accessibility. Prior research in Porto and Kunming has shown that residents may live within the nominal fifteen-minute range yet face fragmented infrastructure and limited multimodal connectivity that undermine the equity ambitions of the fifteen-minute city. The Sintra results reinforce this picture, demonstrating that simple straight-line measures would mask precisely the deficits that matter most to vulnerable, car-dependent, or mobility-limited populations. The authors are candid about their model’s limitations: the constant walking speed does not capture slope-induced effort on steeper segments; the fifteen-minute threshold may overestimate access for elderly residents; pocket parks under half a hectare are underrepresented; and population density, the model’s demand proxy, is not equivalent to socioeconomic vulnerability. Fully substantiating environmental justice claims, they acknowledge, would require integrating income data or a composite Social Vulnerability Index directly into the multi-criteria framework—an extension their weighting structure can readily accommodate.

The practical payoff is a six-stage transferable framework: inventory and assess existing green spaces; model pedestrian access on real networks; identify equity-focused deficits by overlaying accessibility with demographic data; evaluate and prioritise candidate sites with AHP-weighted spatial suitability models; and pursue adaptive planning that verifies ground conditions and integrates selected sites into municipal plans as multifunctional green infrastructure. For Sintra specifically, the recommendations point toward Tapada das Mercês and the other “Category D” zones where medium-high density meets total accessibility deficit. For planners elsewhere, the message is that the fifteen-minute city will remain an aspirational slogan until municipalities replace area-based green space quotas with people-centred, network-based analysis—treating walkable access to nature not as a statistical by-product of protected landscapes, but as a fundamental determinant of urban health to be engineered, measured, and delivered.

Traditionally, accessibility to urban green spaces has been gauged predominantly by geographic metrics—how close a park or garden is to a resident’s home. The authors challenge this narrow view by emphasizing that physical distance alone does not guarantee true accessibility. They argue that factors such as mobility limitations, neighborhood safety, and infrastructural inadequacies play critical roles in shaping how individuals experience green spaces. This paradigm shift invites urban planners to rethink strategies, prioritizing inclusivity that accounts for varying abilities and needs.

Yet, physical barriers are only one facet of the puzzle. The research delves into cultural barriers, revealing how social norms, community dynamics, and historical contexts influence people’s interaction with green spaces. For instance, certain groups may feel unwelcome or alienated in parks due to socio-economic divides or cultural disconnects. The authors document instances where cultural perceptions create invisible walls, discouraging participation and diminishing the benefits that green environments could offer to mental and social well-being.

Equally novel is the focus on emotional barriers, a dimension often overlooked in urban sustainability discourse. Emotional accessibility pertains to how individuals perceive and relate to green spaces on a psychological level. Feelings of anxiety, past traumatic experiences, or mistrust towards certain areas can significantly impede usage, regardless of how accessible these spaces are physically. Understanding this emotional landscape is crucial for creating green environments that foster genuine inclusivity and healing.

A key methodological strength of this study lies in its interdisciplinary approach. The researchers combined geographic information system (GIS) mapping with qualitative interviews and surveys, enabling a nuanced understanding that blends spatial data with human experiences. This holistic methodology allows the team to pinpoint not only where barriers exist but why they persist, thus facilitating targeted interventions that go beyond conventional planning models.

One of the most compelling findings is that urban green spaces are rife with paradoxes. For instance, affluent neighborhoods boast parks that are both physically accessible and culturally resonant for residents, yet they suffer from emotional barriers linked to social pressures or performance anxieties. Conversely, less affluent areas may face significant physical obstacles—such as poor lighting or unsafe pathways—compounded by cultural stigmatization that further alienates potential users. These complexities underscore the need for layered, context-sensitive solutions.

The study also critically examines the implications of these barriers on health disparities. Urban green spaces have long been championed for their contributions to reducing stress, encouraging physical activity, and improving cognitive function. However, when accessibility is uneven, these health benefits become unevenly distributed, exacerbating existing inequalities. By mapping accessibility in relation to demographic data, the authors shed light on how systemic inequities are entrenched within the urban fabric.

In response, the research suggests innovative policy frameworks that integrate social equity into green space planning. These frameworks advocate for community engagement processes that are authentic and inclusive, ensuring that voices from diverse populations inform design and management. Furthermore, participatory design is proposed as a tool to co-create spaces that resonate culturally and emotionally, fostering ownership and sustained utilization.

Technological advancements feature prominently in the study’s recommendations. Emerging smart city tools, such as sensor networks and augmented reality, could be harnessed to tailor green space experiences dynamically. For example, real-time data on crowd density or environmental quality could help mitigate emotional barriers by providing users with a sense of control and safety. However, the authors caution against excessive reliance on technology without concurrently addressing underlying social and cultural challenges.

Importantly, the paper calls attention to the transformative potential of urban green spaces amid global challenges such as climate change and rapid urbanization. By dismantling the triad of physical, cultural, and emotional barriers, cities can foster resilient, healthy, and socially cohesive environments. Green spaces reimagined through this inclusive framework could become sanctuaries that nurture biodiversity and human well-being simultaneously.

As cities worldwide strive for sustainability, this research signals a pivotal shift toward human-centered urbanism. It emphasizes that inclusive accessibility is not just a technical issue but a deeply social one, intertwined with identities, histories, and aspirations. Implementing these insights demands commitment from stakeholders across sectors—urban planners, policy-makers, public health officials, and communities themselves—to realize green spaces as truly democratic commons.

The study also highlights future research directions, advocating for longitudinal studies that monitor how interventions impact accessibility over time. Furthermore, there is a call to integrate accessibility metrics into broader sustainability assessments and urban governance frameworks. Such integration would ensure that policies are responsive to the lived realities of diverse populations and adaptable to evolving urban contexts.

In addition, the authors underscore the importance of education and awareness campaigns to dismantle cultural stigmas and encourage inclusive usage. These efforts could foster emotional connections to green spaces, enhancing community cohesion and collective stewardship. The intersection of ecological sustainability with social justice, argued here, becomes the cornerstone for the cities of tomorrow.

In conclusion, the work by Abdulla and colleagues reframes urban green space accessibility through a rich, interdisciplinary lens. By exposing and addressing physical, cultural, and emotional barriers, their study lights a path toward more equitable and sustainable urban futures. Their insights beckon a reimagining of green infrastructure, one that fully embraces the diversity of human experience within the complexity of the urban ecosphere.

Subject of Research: Barriers to accessibility of urban green spaces including physical, cultural, and emotional factors.

Article Title: Redefining accessibility: uncovering physical, cultural, and emotional barriers to urban green space accessibility.

Article References:
Abdulla, Z., Albadra, D., McCullen, N. et al. Redefining accessibility: uncovering physical, cultural, and emotional barriers to urban green space accessibility. npj Urban Sustain 5, 107 (2025). https://doi.org/10.1038/s42949-025-00293-x

Image Credits: AI Generated

DOI: https://doi.org/10.1038/s42949-025-00293-x