Priority areas to protect mangroves and maximise ecosystem services

Ecosystems provide essential services such as food, air and water purification, and climate mitigation, but these services are threatened by biodiversity loss from human activities. International targets (Aichi Target 11) aimed to protect portions of terrestrial and marine areas, and new goals (post-2020 Global Biodiversity Framework) call for 30% protection. Conservation planning has often neglected ecosystem services, focusing on biodiversity representation while minimizing conflicts with economic activities. Mangroves, located at the land-sea interface, deliver key services including coastal protection, carbon storage, and fisheries support, yet global priority areas that jointly safeguard mangrove biodiversity and ecosystem services have not been identified. The study aims to: (1) assess how well current protected areas represent mangrove biodiversity and ecosystem services; (2) identify areas that, if efficiently protected, ensure conservation of mangrove biodiversity and maximize ecosystem services while minimizing area; and (3) identify priority areas for expansion of mangrove protection. The focus is on prioritizing benefits to local people by including ecosystem services in spatial planning, acknowledging that global analyses should inform but not replace local management.

Recent spatial planning research increasingly integrates ecosystem services with biodiversity conservation. Jung et al. identified terrestrial areas important for biodiversity, carbon, and water; Sievers et al. mapped co-occurrence of mangrove biodiversity and services; Sala et al. explored ocean co-benefits, though aspects were critiqued. At local and regional scales, studies evaluate trade-offs among ecosystem services and include them in analyses. Despite this progress, few studies have globally identified priority coastal areas safeguarding both biodiversity and services. For mangroves, prior work documents their roles in coastal protection, sediment dynamics, carbon storage (with higher per-area storage than many other ecosystems), and fisheries/nursery functions. However, global prioritization that explicitly includes multiple mangrove ecosystem services alongside biodiversity targets has been lacking.

Study area comprised the global mangrove distribution (137,600 km²) from Global Mangrove Watch (GMW, 2016). The analysis used 9,111 hexagonal planning units at 20-km alongshore resolution (20 km inland extent), in an equal-area Mollweide projection. Biodiversity data included: (1) geographic ranges for 65 common mangrove species from IUCN, intersected with 25-m GMW to produce high-resolution species presence; (2) mangrove biophysical typologies (geomorphic and sedimentary classes) from Worthington et al.; and (3) marine provinces from Spalding et al. Species distributions were split across typologies and provinces, yielding 944 sub-features, each assigned a conservation target via log10-linear interpolation: species with ranges <10,000 km² target 100% representation; >250,000 km² target 10%, with interpolation between, following Rodrigues et al. This ensures higher targets for small-range species and representation across environmental heterogeneity. Existing protected areas were from WDPA, cleaned per best practices; planning units with ≥50% of mangrove area under protection were considered protected. Two protection baselines were used: strictly protected (IUCN I–IV) and all protected (I–VI and unclassified). Ecosystem services included: coastal protection benefits to people and properties (Menéndez et al.), carbon stocks (aboveground biomass from Simard et al. and soil carbon from Sanderman et al.), and fisheries benefits proxied by fishing intensity (fisher days km−2 yr−1 from zu Ermgassen et al.). Datasets were harmonized to planning units using nearest-neighbor interpolation; coastal protection values were normalized per km² of mangrove and scaled by mangrove area within each unit. Spatial prioritization was conducted using the prioritizr R package with Gurobi (optimality gap 0.01%). The cost of selecting a planning unit was its mangrove area. A series of nested optimizations ran with incremental area budgets from 1% to 100% of global mangrove area (or starting from 14% when adding to current strictly protected areas and from 44% when adding to all protected areas). Objectives minimized shortfall in biodiversity targets while also maximizing ecosystem services by including each service as a feature with a 100% target. Alternative runs optimized for biodiversity only to compare efficiency, and weighted runs increased selection probability for ecosystem services (weights 10, 100, 1000). Agreement between solutions was assessed via Cohen’s Kappa. Outputs included rankings of planning units, efficiency curves for targets reached and service amounts conserved, and analyses by continent and country.

• Current protection: Strictly protected areas (IUCN I–IV) cover 13.5% of global mangrove distribution; including all categories brings protection to 43%. Coverage varies: Americas 24.7% strictly protected, Oceania 11.1%, Asia 10.9%, Africa 3.5%. Eleven countries protect >70% of mangroves strictly, but 67 protect <10%.
• Ecosystem services currently conserved within strictly protected areas (13.5% of mangrove area): 24.9% of global coastal property value safeguarded (~$12.0 billion); 14.5% of global stored carbon (980.8 Tg C); 6.8% of people safeguarded (0.64 million); 6.2% of fisheries benefits (11.1 million fisher days yr−1). This indicates avoidance of densely populated and high-fishing areas in past siting.
• Coverage of priority areas: Only 4.9% of high-priority and 12.1% of mid-priority areas (for biodiversity and services) fall within current strictly protected areas. Current protection meets just 6.8% (64/944) of the species-by-context conservation targets; no species meets all targets.
• Expansion to 30% protection (adding to current strictly protected areas) concentrates new priority areas in Asia (63.6%) and Oceania (17.0%); largest national needs in Indonesia (30.1% of added area), Papua New Guinea (10.5%), India (9.5%), Panama (5.3%), Thailand (5.0%).
• Additional ecosystem services from 30% expansion: +$16.3 billion coastal property value (33.7% of global amount represented by mangroves), +6.1 million people safeguarded (64.8%), +1173.1 Tg C stored (17.4%), +50.7 million fisher days yr−1 (28.6%). Major contributors include India (+$6.1B; +2.1M people; +14.3M fisher days), China (+$3.7B), Vietnam (+2.9M people), Indonesia (+460.0 Tg C), Papua New Guinea (+156.0 Tg C), Bangladesh (+7.0M fisher days).
• Efficiency and overlap: Biodiversity-only vs biodiversity+services solutions are highly congruent (Cohen’s Kappa ~0.7). At a 30% total protection level, targets reached are similar: 81.0% (biodiversity-only) vs 80.0% (biodiversity+services). Early-selected units yield rapid gains for people and property protection; carbon increases more linearly due to narrow value distribution.
• If current strictly protected areas are ignored, selecting the top 13% of mangrove area would reach 44.9% of targets, far exceeding the 6.8% reached by the existing 13.5%. At 50% protection, 99.5% (939/944) of targets are met without starting PAs; 99.0% when adding to existing strictly protected areas.
• Prioritized areas have higher mean values for people safeguarded and fishing intensity than currently protected areas; carbon and property values are similar between prioritized and current protected units.

The analysis shows substantial gaps in how current protected areas capture mangrove biodiversity and ecosystem services, especially in Asia and Oceania where biodiversity and human dependence are high. Existing protection underrepresents high-priority areas and targets, likely due to historical emphasis on minimizing socioeconomic conflicts, which placed protected areas away from dense populations and fishing grounds. Strategic expansion to 30% can deliver large human benefits—coastal risk reduction for people and property, fisheries support—while achieving biodiversity representation comparable to biodiversity-only plans. The high congruence between biodiversity and services suggests that areas of greater species richness and functional diversity often provide multiple services. Including ecosystem services in spatial prioritization yields more benefits to local communities without substantial efficiency loss in biodiversity outcomes. However, many priority areas are near urban centers, where management is challenging due to pressures such as clearing, fragmentation, and altered water quality. The study advocates for support to developing countries housing most priority areas, potentially financed by higher-income nations whose consumption drives biodiversity and carbon losses elsewhere. It also emphasizes that protecting natural mangroves is more effective and provides higher services than restoration alone, though restoration remains important. Integrating ecosystem services more broadly in conservation planning—especially where biodiversity-service links are strong (e.g., coastal ecosystems)—can align human wellbeing with conservation goals.

Including ecosystem services explicitly in mangrove conservation prioritization identifies priority areas that can simultaneously meet biodiversity targets and maximize human benefits, with little to no additional protected area required compared to biodiversity-only planning. Expanding protection to 30% of global mangrove area could safeguard billions in coastal property value, protect millions of people from flooding, secure substantial carbon stocks, and support fisheries. The study provides a global framework and maps to inform national and regional planning, NGO priorities, and stakeholder engagement. Future research should incorporate protection costs and trade-offs, improve spatial resolution and local relevance of biodiversity and ecosystem service data, include additional services (e.g., tourism, water filtration, cultural values), account for risks and spatial patterns of loss, refine fisheries metrics beyond fishing intensity, and consider diverse governance mechanisms beyond formal protected areas.

• Costs of protection were not quantified; future analyses should evaluate cost–benefit trade-offs.
• Biodiversity and ecosystem service datasets are relatively coarse and may not capture fine-scale variation; global results should guide, not dictate, local planning.
• Protected area inclusion used a ≥50% mangrove coverage threshold per planning unit; differing thresholds may alter results.
• Inclusion of coastal risk reduction and fisheries benefits biases selection toward mangroves near urban areas; remote areas may better support biodiversity due to lower human pressures.
• Fisheries proxy (fishing intensity) may not reflect catch or supply; dataset did not account for protection status (potential overestimation in no-take MPAs) and lacked some regional expertise.
• Ecosystem service layers did not differentiate services among mangrove species/assemblages and may overlook cryptic ecological degradation.
• The analysis focused on protected areas; other effective area-based conservation measures, indigenous/community conserved areas, and payment schemes were not modeled but can deliver positive outcomes.