Mangroves, such as Avicennia marina and Rhizophora apiculata, form coastal bioshields that protect against erosion and storms, requiring careful site selection, species diversity, and community involvement for sustainable restoration (Selvam et al., 2005). In extreme environments like arid coastal zones and sabkhas, high salinity (>40 ppt) disrupts osmotic balance and induces ion toxicity, while scarce freshwater and high evaporation trigger drought stress, impairing photosynthesis, water uptake, and metabolic processes (Munns and Tester, 2008; Fan et al., 2024; Abdelkader et al., 2024). These stressors challenge mangroves, vital agroecological systems that provide blue carbon storage, shoreline stabilization, and biodiversity conservation, yet face growing threats from climate change and anthropogenic pressures (Teutli Hernández et al., 2020). This study explores how mangroves’ physiological adaptations enable resilience in harsh coastal ecosystems, informing strategies for effective restoration and coastal protection.

Mangrove restoration in extreme environments such as sabkhas presents a transformative, nature-based solution for advancing carbon sequestration, coastal resilience, and ecosystem functionality in arid regions. In Saudi Arabia’s hyper-arid coastal zones, Avicennia marina (gray mangrove) predominates, renowned for its exceptional tolerance to hypersalinity (>40 ppt), extreme aridity, and temperature fluctuations (Chang et al., 2020; Shaltout et al., 2021). However, challenges such as hypersaline, nutrient-deficient soils, scarce freshwater, and anthropogenic pressures—including industrial pollution and coastal development—jeopardize its persistence. These stressors necessitate innovative, evidence-based strategies in soil management, hydrological engineering, and vegetation establishment to strengthen coastal ecosystems against climate change impacts. Sabkha conversion—transforming barren, salt-crusted coastal flats into productive mangrove habitats—remains a largely untapped frontier, with sparse research on its long-term efficacy, underscoring the urgency of adapting insights from naturally occurring sabkha mangroves to inform scalable restoration frameworks.

This review synthesizes cutting-edge approaches to enhance Avicennia marina survival in coastal zones and sabkhas, spotlighting their pivotal role in scaling nature-based solutions for decarbonization and sustainable development. It evaluates tailored strategies for establishing Avicennia marina in arid, hypersaline coastal environments, with a novel focus on sabkha conversion as a pioneering restoration approach to amplify ecosystem services and support global decarbonization goals. The review investigates critical factors for successful mangrove establishment, including soil amendments, seedling preconditioning, optimized tidal inundation, protective shading, and advanced nursery techniques, drawing on case studies without conducting a quantitative meta-analysis. Key findings indicate that irrigation with moderate salinity (15–25 ppt) enhances survival and growth, achieving 85% germination at 15 ppt (Lebda et al., 2024), while nutrient-enhanced soils via NPK fertilization boost biomass by 35–45% (Osman and AboHassan, 2010). Growth metrics vary widely: Seedling heights range from 25 cm (Santos et al., 2021) to 173.3 cm (Alrubaye et al., 2023) over 9–24 months, with mature stands reaching 3–5 m (Mousavi et al., 2024). Survival rates span 18–85%, with short-term trials (e.g., 75% at 2 years; Erftemeijer et al., 2021) outperforming long-term studies (e.g., 26% at 30 years; Erftemeijer et al., 2020). Carbon storage estimates range from 18.2 to 78 Mg C ha⁻¹, with natural stands (e.g., 78 Mg C ha⁻¹; Alsumaiti and Shahid, 2019) exceeding transplants (e.g., 18.2–32.7 Mg C ha⁻¹; Naser, 2023). Statistical assessments, such as ANOVA and L. S. D. tests (p < 0.05), are inconsistently applied across studies, with some (e.g., Chang et al., 2020) reporting significant differences in biomass (p < 0.05) while others (e.g., Mousavi et al., 2024) lack statistical rigor, complicating comparability.

Methodological heterogeneity across studies—ranging from observational (e.g., Mousavi et al., 2024, assessing natural stands without controls) to experimental designs (e.g., Santos et al., 2021, using controlled salinity gradients)—further complicates synthesis. Observational studies, such as Mousavi et al. (2024) and Shaltout et al. (2021), provide ecological snapshots (e.g., 500–1,500 trees ha⁻¹, 28.9 Mg C ha⁻¹) but lack causal inference due to absent experimental controls. Experimental studies, such as Lebda et al. (2024) and Alrubaye et al. (2023), offer controlled insights (e.g., 85% germination at 15 ppt and 44% survival in industrial zones) but often use small sample sizes (30–50 seedlings) or limited replication (1–3 plots), reducing statistical power (e.g., power <0.8 for detecting 10% survival differences). Study quality varies: High-quality experimental designs (e.g., Chang et al., 2020) use robust sampling (n = 3 plots, 10–20 trees per plot) and statistical tests (ANOVA, p < 0.05), while observational studies (e.g., Mousavi et al., 2024) often omit sample sizes or statistical validation, risking bias. Long-term studies (e.g., Erftemeijer et al., 2020, n = 500,000 seedlings) reveal lower survival (26%) due to cumulative stressors, contrasting with short-term trials (e.g., Bhat et al., 2004, n = 50–100, 60–70% survival), highlighting the need for extended monitoring to assess true efficacy.

The economic feasibility of carbon credits or blue carbon remains speculative as no case study provides comprehensive cost analysis or cost–benefit assessments. Al-Guwaiz et al. (2021) estimate potential revenues of $5,000–$10,000 ha⁻¹ over 10 years from carbon credits ($5–$50 per t CO₂e) in Yanbu, Saudi Arabia, but lack detailed cost breakdowns (e.g., $25,000 ha⁻¹ for restoration). Erftemeijer et al. (2020) note high initial costs for tidal channels ($5,000–$15,000 ha⁻¹) without quantifying carbon revenue, while Lewis and Brown (2014) cite maintenance costs ($2,000–$5,000 ha⁻¹ yr.⁻¹) without linking to market returns. The absence of net present value (NPV) calculations or break-even analyses undermines claims of economic viability, necessitating pilot projects to validate carbon offset potential and integrate co-benefits (e.g., fishery yields, $500–$1,000 ha⁻¹ yr.⁻¹; Ravaoarinorotsihoarana et al., 2023).

Aligned with frameworks such as the UN Decade on Ecosystem Restoration, the Saudi Green Initiative (SGI) and Middle East Green Initiative (MGI), launched in 2021 by Saudi Arabia, provide a regional framework for such efforts: SGI aims to reduce emissions, plant 10 billion trees, and protect 30% of Saudi Arabia’s land and sea by 2030, while MGI fosters regional collaboration to plant 50 billion trees, reduce carbon emissions by over 60% from hydrocarbon production, and restore 200 million hectares of degraded land across the Middle East and North Africa, supporting global climate goals and offering scalable models for mangrove restoration in arid regions (Saudi Green Initiative, 2024). By addressing knowledge gaps through a systematic synthesis of case studies, this review aims to inform scalable, evidence-based restoration frameworks to enhance Avicennia marina resilience and ecosystem services in some of the world’s most challenging environments.

A systematic literature review was undertaken to assess the evidence supporting Avicennia marina restoration in hypersaline, arid regions, following the scoping review framework by Arksey and O’Malley (2005) and adhering to the PRISMA checklist for reporting. The review process involved five key stages: (a) defining the research question and objectives to explore factors affecting A. marina restoration, specifically focusing on salinity tolerance, nutrient management, soil amendments, hydrological optimization, and carbon sequestration; (b) conducting an extensive search for relevant studies in Scopus, Web of Science, PubMed, and Google Scholar, covering publications from 2000 to 2025, using keywords such as “Avicennia marina,” “mangrove restoration,” “hypersaline,” “arid coast,” “salinity tolerance,” “nutrient management,” “soil amendments,” “carbon sequestration,” and “sabkha conversion,” combined with Boolean operators (e.g., “Avicennia marina” AND “hypersaline”); (c) screening and selecting studies by two independent researchers to eliminate duplicates, initially evaluating titles, abstracts, and conclusion, followed by a full-text review, resulting in 55 studies selected from an initial pool of 144, based on their relevance to A. marina restoration in arid, hypersaline environments, with a focus on experimental designs, field-based studies, and case studies from regions such as the Middle East, Red Sea, and Persian Gulf; (d) extracting quantitative data, including survival rates (70–80%), growth metrics, biomass production (40 Mg ha⁻¹), and carbon sequestration (28–45 Mg C ha⁻¹); and (e) synthesizing results through comparative analysis, presented in tabular format (Table 1) and a PRISMA flowchart (Figure 1), with inclusion criteria requiring studies to be peer-reviewed, published between 2000 and 2025, and providing measurable ecological outcomes, while excluding non-peer-reviewed sources, pre-2000 studies, and those lacking quantitative restoration data or focusing on non-arid, non-hypersaline settings. This review addresses gaps and inconsistencies in A. marina restoration, delivering a thorough synthesis of evidence-based strategies. By clarifying the interplay of salinity tolerance, nutrient management, hydrological optimization, and carbon sequestration, this study informs the development of effective restoration practices and climate change mitigation approaches, highlighting the critical role of these factors in bolstering the resilience of arid coastal ecosystems and underscoring the need to integrate A. marina restoration into global climate frameworks to tackle urgent environmental challenges.

Mangroves in arid, hypersaline coastal zones endure severe stressors such as extreme salinity, waterlogging, tidal fluctuations, nutrient deficiencies, and microbial influences, all of which challenge their survival and growth. Avicennia marina, a dominant species in regions such as the Red Sea, Persian Gulf, and Arabian Gulf, showcases exceptional resilience through its salt-secreting glands and physiological adaptations, making it well-suited for stress-prone environments such as sabkhas (Chang et al., 2020). This section synthesizes findings from 23 studies across the Middle East, Red Sea, Persian Gulf, and other arid zones, examining how salinity gradients, dual stressors (e.g., salinity and waterlogging), microbial impacts (e.g., H₂S production), and hydrological conditions shape A. marina’s germination, establishment, and growth, offering critical insights for restoration in extreme environments (Table 1). A. marina thrives in sandy soils (50–90% sand) with moderate silt and clay, typically associated with Entisols and Fluvisols, but sabkha environments pose significant challenges due to extreme salinity—electrical conductivity (EC) reaches 20,800 μS/cm, compared to 46,200 μS/cm in Arabian Gulf water, often exceeding 10 times seawater salinity (Al-Mhaidib, 2003). Although A. marina tolerates EC levels of 10,000–40,000 μS/cm (6,400–25,600 ppm), sabkha measurements are unreliable due to low organic matter (0.1–1%), which disrupts sensor accuracy and masks true salinity levels (Al-Mhaidib, 2003). The species adapts to high sodium (78.8‰ in sabkha water vs. 100–1,000 ppm tolerance) and chlorine (157.2‰ vs. 100–1,000 ppm tolerance), endures pH levels from 6.5 to 8.0 despite sabkha’s acidic pH of 6.9, and survives with limited nutrients—tolerating low organic matter (0.1–1%) and total nitrogen as low as 500 ppm—although optimal growth occurs at 1–5% organic matter, improving nutrient retention and cation exchange capacity (CEC) (Chang et al., 2020; Al-Mhaidib, 2003). A CEC range of 5–50 meq/100 g is ideal, yet A. marina persists at lower values, providing a buffer against nutrient stress. Micronutrient stress is managed through tolerance to iron fluctuations (500–3,000 ppm vs. trace amounts in sabkha water) and trace metals such as cadmium (<3–8 ppm) and lead (<70 ppm), but sulfide accumulation—exacerbated by H₂S from algal decomposition in sabkhas—beyond 50 ppm can be toxic, necessitating careful site selection (Al-Mhaidib, 2003). Essential micronutrients such as zinc (optimal at 10–50 ppm), manganese, boron, and molybdenum support A. marina’s stress physiology, particularly zinc’s role in enzymatic functions.

Avicennia marina (Forssk.) Vierh. stands as a formidable carbon sink in arid, hypersaline coastal regions, where natural stands consistently outperform transplanted sites, offering significant potential for climate mitigation despite environmental stressors such as hypersalinity, industrial pollution, and hydrodynamic energy (Alsumaiti and Shahid, 2019; Naser, 2023). This review synthesizes evidence from 12 studies to evaluate A. marina’s carbon sequestration capacity, restoration outcomes, and the critical factors influencing its success in challenging environments such as the Arabian Gulf, Persian Gulf, and Australian coasts. In Abu Dhabi, Alsumaiti and Shahid (2019) reported 78 Mg C ha⁻¹ across eight sites (40 ppt salinity), with 25.2 Mg C ha⁻¹ in biomass (35.4 Mg ha⁻¹ above-ground and 14.6 Mg ha⁻¹ below-ground) and 52.8 Mg C ha⁻¹ in soil, driven by dense stands (1,500 trees ha⁻¹) and organic-rich sediments. Naser (2023) documented 45.6 Mg C ha⁻¹ in Bahrain’s natural stands (52.3 Mg C ha⁻¹ at Tubli Bay), while transplanted sites (5–15 years) ranged from 18.2 to 32.7 Mg C ha⁻¹, reaching 70% of natural levels after 15 years, highlighting a time lag for carbon stock accumulation. Erftemeijer et al. (2020) estimated ~40 Mg C ha⁻¹ (biomass-based) in Abu Dhabi, aligning with regional averages of 28.9 Mg C ha⁻¹ (Shaltout et al., 2021), while Alrubaye et al. (2023) in Iraq’s industrial Khor Al-Zubair port inferred similar potential despite a 44% survival rate. Sabkha environments, however, pose severe constraints, with salinity levels reaching ~239 ppt (157.2‰ Cl⁻, 78.8‰ Na⁺), EC at 20,800 μS/cm, and an acidic pH of 6.9, coupled with H₂S toxicity from algal decomposition, reducing survival to below 20% and growth by 20–30%, thereby limiting carbon sequestration potential (Al-Mhaidib, 2003; Chang et al., 2020; Ball and Critchley, 1982). Carbon sequestration is heavily influenced by site conditions and management strategies, with natural stands benefiting from dense, organic-rich sediments and tidal flushing that enhance soil carbon (52.8 Mg C ha⁻¹) and biomass accumulation (40 Mg ha⁻¹) (Alsumaiti and Shahid, 2019; Erftemeijer et al., 2020; Ghasemi et al., 2012), whereas industrial pollution and hypersalinity diminish capacity—Ali et al. (2009) reported a 50% canopy loss or complete die-off in Al Jubail due to hypersalinity (>50 ppt), nutrient-poor soils, and heavy metals (e.g., 50 mg kg⁻¹ Pb). Soil management is pivotal, as Bhat and Suleiman (2004) found sandy, well-drained Typic Torriorthents yielding 70% survival and 1.5 m height, compared to 50% in clay-rich, saline Typic Aquisalids. A. marina’s physiological plasticity underpins its success, with Ball and Critchley (1982) demonstrating high-light seedlings achieving a light-saturated photosynthesis rate (Pmax) of 12 μmol CO₂ m⁻² s⁻¹, thicker leaves, and lower chlorophyll (300 μg cm⁻²) for open coasts, while low-light seedlings exhibit higher quantum yield (0.06 mol CO₂ mol⁻¹ photons) and chlorophyll (500 μg cm⁻²) for shaded zones, complemented by salt glands and aerial roots that tolerate 40–48 ppt salinity and waterlogging (Erftemeijer et al., 2020). Furthermore, A. marina’s growth under varying light and intertidal conditions supports its potential in mixed mangrove forests, with Jiang et al. (2019) showing that higher intertidal elevation and moderate light levels enhance early growth under Sonneratia apetala canopies, suggesting its suitability for transitioning monoculture plantations to diverse ecosystems. Environmental stressors significantly impact outcomes, with Hurst et al. (2015) noting hydrodynamic energy reducing survival (1–76%) and growth (−0.83 to 10.45 mm/month) in exposed temperate sites, and Van Loon et al. (2016) and van Bijsterveldt et al. (2022) emphasizing optimal inundation (<50 cm) for Avicennia alba and A. marina, with hypersalinity (>60 ppt) causing sharp declines. Industrial runoff, including heavy metals and oil, further exacerbates stress (Ali et al., 2009; Alrubaye et al., 2023), necessitating pre-planting soil remediation (Table 3). Active interventions—such as irrigation (75% survival, Erftemeijer et al., 2021), nursery pre-growth (44–70% survival, Alrubaye et al., 2023; Bhat and Suleiman, 2004), and tidal channels (26% survival, 40 Mg ha⁻¹ biomass, Erftemeijer et al., 2020)—leverage A. marina’s adaptations to achieve higher short-term success in hypersaline conditions (40–48 ppt), while engineered solutions mimic natural hydrology to promote long-term stability and carbon sequestration (40–78 Mg C ha⁻¹). However, low survival in high-stress sites (18–26%) and sabkha constraints highlight the need for sheltered, low-energy conditions and advanced strategies such as salinity dilution to 15–30 ppt, pH buffering, and aeration to counter H₂S toxicity (Al-Mhaidib, 2003). Future research should focus on quantifying carbon sequestration in restored sites over longer periods, developing scalable soil management practices, and addressing industrial pollution to fully harness A. marina’s climate mitigation potential in arid, hypersaline coastal environments.

Restoration of Avicennia marina (Forssk.) Vierh. in arid, hypersaline coastal regions is shaped by complex environmental stressors, necessitating a nuanced understanding of physiological responses, quantitative outcomes, and ecological trade-offs to inform effective strategies (refer to Figure 2: Flowchart for A. marina restoration planning). Quantitative effect size analyses reveal significant variability across life stages and stressors: Lebda et al. (2024) reported a sharp decline in germination rates from 85% at 15 ppt to 20% at 60 ppt (Cohen’s d ≈ 2.1, assuming 10% standard deviation), underscoring salinity’s pronounced impact on early development, while Chang et al. (2020) demonstrated mature trees’ resilience, with above-ground biomass increasing from 7.33 Mg ha⁻¹ at 15 ppt to 41.44 Mg ha⁻¹ at 45 ppt (d ≈ 1.2, assuming 5 Mg ha⁻¹ standard deviation). Dual stressors amplify these effects, as Xiao et al. (2022) found survival dropping from 90% at 30 ppt and 33% submergence to 20% at 45 ppt and 66% submergence (d ≈ 1.8), highlighting submergence’s exacerbating role. Restoration techniques vary in efficacy—transplantation with irrigation achieved 75% survival compared to 26% with tidal channels alone (d ≈ 1.5; Erftemeijer et al., 2020, 2021), while nursery pre-growth yielded 44% survival (d ≈ 0.8; Alrubaye et al., 2023)—emphasizing the need for active hydrological management. Optimal salinity differs by life stage (15–30 ppt for germination, 40–45 ppt for mature trees), with nutrient-rich tidal inputs (0.15% total nitrogen) enhancing biomass under hypersalinity, although pre-growth mitigates short-term nutrient limitations (Chang et al., 2020; Alrubaye et al., 2023). Sabkha environments introduce extreme challenges, with salinity levels reaching ~239 ppt (157.2‰ Cl⁻, 78.8‰ Na⁺), EC at 20,800 μS/cm, and an acidic pH of 6.9, coupled with H₂S toxicity from algal decomposition, reducing survival to below 20% and growth by 20–30%, far exceeding A. marina’s tolerance thresholds (Al-Mhaidib, 2003; Chang et al., 2020; Ball and Critchley, 1982). Interactions between salinity, nutrients, and elevation are critical, with significant salinity × nutrient (p < 0.05) and salinity × elevation (p < 0.01) effects necessitating integrated approaches that leverage tidal connectivity and elevation adjustments to mitigate stress (Corona-Salto et al., 2024; Shaltout et al., 2021). Practical challenges further complicate restoration: Transplantation with irrigation, while effective, is costly ($10,000–$20,000 ha⁻¹), whereas tidal channel excavation ($5,000–$10,000 ha⁻¹) offers a cost-effective alternative, promoting sediment accretion (2–3 mm yr.⁻¹) but with lower initial survival (Erftemeijer et al., 2020). Nursery pre-growth is the least expensive ($2,000–$5,000 ha⁻¹) but vulnerable to industrial pollutants, requiring site remediation (Alrubaye et al., 2023). Ecological risks include eutrophication from fertilization, monospecific plantations reducing biodiversity (48 vs. 60 + bird species in natural forests; Mousavi et al., 2024), and pollutant release from channel excavation (Ali et al., 2009). Climate change exacerbates these challenges, with sea-level rise (1– (1–3.7 mm yr.⁻¹; Intergovernmental Panel on Climate Change, 2021) and rising temperatures (e.g., 40°C + in Kuwait) intensifying stress, necessitating adaptive strategies such as elevation techniques and brackish site selection (15–30 ppt). A. marina’s physiological adaptations—salt glands (Fv/Fm: 0.77 at 45 ppt), aerial roots, and photosynthetic plasticity (Pmax: 12 μmol CO₂ m⁻² s⁻¹ in high light)—underpin its resilience, guiding site-specific restoration designs that balance light, salinity, and inundation for optimal outcomes (Reef et al., 2019; Ball and Critchley, 1982). Future efforts should focus on cost-effective, multi-stressor management, integrating sabkha-specific interventions (e.g., salinity dilution, pH buffering, and aeration to counter H₂S toxicity), and long-term monitoring to enhance A. marina’s restoration success in arid coastal ecosystems.

Nutrient availability, environmental stressors, and restoration strategies are pivotal in shaping the growth, survival, and ecological dynamics of mangrove ecosystems, particularly in nutrient-scarce or anthropogenically impacted coastal regions, where Avicennia marina (Forssk.) Vierh. demonstrates remarkable adaptability (Naidoo, 2009; Almahasheer et al., 2016; Almahasheer et al., 2013; Almahasheer, 2021). This review synthesizes findings from 17 studies across diverse regions—including the Central Red Sea, Western Saudi Arabia, Vamleshwar (India), Iran, Bahrain, and global contexts—to explore nutrient enrichment effects, ecological interactions, and restoration approaches for A. marina and related species such as Sonneratia alba, Rhizophora mucronata, and Avicennia germinans (Table 4). Nitrogen (N) emerges as a primary limiting nutrient in arid, saline environments, with Naidoo (2009) reporting significant increases in stem height, leaf production, and biomass in A. marina under N enrichment (ammonium nitrate, low to high levels) in a 12-month greenhouse experiment (25% seawater, 20–28°C), while phosphorus (P) had negligible effects. Similarly, Almahasheer et al. (2016) found N enrichment (100 g m⁻²) in the Central Red Sea (40–45 ppt salinity, <50 mm rainfall) boosted leaf N content, chlorophyll, and growth in A. marina, with minimal P impact due to sufficient P in carbonate soils (N:p < 14). Osman and AboHassan (2010) demonstrated synergistic NPK effects near Jeddah, Saudi Arabia (38–42 ppt, <100 mm rainfall), with NPK (50 g N, 25 g P, 20 g K m⁻²) increasing stem height by 35% and biomass, compared to 20% with N-only. However, Lovelock et al. (2009) highlighted risks of over-enrichment in Moreton Bay, Australia (25–35 ppt, 1,000 mm rainfall), where high N (200 g m⁻²) and P (100 g m⁻²) reduced A. marina survival by 40 and 25%, respectively, due to toxicity (soil N: 0.1%). Nitrogen fertilization also enhances physiological resilience, as Martin et al. (2010) showed high N (5 mM) improving water-use efficiency, photosynthetic rates, and biomass in juvenile A. marina under high salinity (75% seawater), while Naidoo (1987) reported 5 mM N mitigating salinity stress (50% salinity), increasing growth by 40–50%. Seedling success benefits from balanced NPK, with Miah and Moula (2019) noting 45–50% height and 60–70% biomass increases in A. marina seedlings in Bangladesh (50 mg N, 25 mg P, 20 mg K/plant). Spatial and temporal nutrient dynamics further influence restoration, as Kumar et al. (2011) found higher N and P uptake in A. marina during monsoon in Vamleshwar, India, and Guo et al. (2018) reported mixed planting in Fujian, China (15–25 ppt), increasing total organic carbon (TOC: 1.5%) and total nitrogen (TN: 0.12%) compared to monocultures (TOC: 1.2%, TN: 0.09%). Microbial and physico-chemical factors also play a role, with Hsiao et al. (2024) showing A. marina root microbiomes in Rabigh, Saudi Arabia (40–45 ppt), driven by forest zonation and root type (e.g., Marinobacter in seaward zones and Rhizobium in fine roots), remaining resilient to chronic N and P enrichment (soil N: 0.08%). Romero et al. (2012) noted N enrichment (100 g m⁻² yr.⁻¹) in Belize reducing N₂ fixation by 50–70% in A. germinans, while P (50 g m⁻² yr.⁻¹) increased it by 20–30%. Environmental stressors such as heavy metals and hydrology challenge restoration, with Abou Seedo et al. (2017) reporting Pb (45 mg/kg) and Cu (60 mg/kg) accumulation in A. marina at Tubli Bay, Bahrain, and Corona-Salto et al. (2024) showing elevation (20–30 cm) in Veracruz, Mexico, enhancing A. germinans survival (70% vs. 40%) and growth (50%) by increasing N (0.06%) and redox potential (+150 mV). Sabkha environments exacerbate these challenges, with extreme salinity (~239 ppt), EC (20,800 μS/cm), acidic pH (6.9), and H₂S toxicity from algal decomposition reducing A. marina growth by 20–30% and survival to below 20%, necessitating interventions such as salinity dilution, pH buffering, and aeration (Al-Mhaidib, 2003; Chang et al., 2020). Collectively, these studies advocate for tailored nutrient management—prioritizing N in arid, N-limited systems, using balanced NPK for seedlings, and leveraging mixed planting and elevation adjustments—while highlighting the risks of over-enrichment, pollution, and sabkha constraints, guiding sustainable restoration strategies for mangrove ecosystems in challenging coastal environments (Table 4).

Avicennia marina (Forssk.) Vierh. exhibits exceptional adaptability to the arid, hypersaline conditions of regions such as the Persian Gulf and Red Sea, characterized by extreme salinity (15–45 ppt) and minimal rainfall (<100 mm yr.⁻¹), making it a cornerstone species for coastal restoration and climate mitigation (Figure 2; Table 5). A synthesis of 55 studies reveals its physiological resilience, driven by salt-secreting glands that enable germination at 15 ppt (85% success; Lebda et al., 2024) and robust growth at 45 ppt, with above-ground biomass reaching 41.44 Mg ha⁻¹ in Qatar’s Al-Thakira forest (Chang et al., 2020). Tidal flushing mitigates hypersalinity by maintaining soil salinity below 50 ppt, as seen in Al Jubail, where exceeding this threshold resulted in complete mortality (Ali et al., 2009), while dual stressors such as prolonged submergence (>66%) and waterlogging reduce survival by 20% by limiting root aeration (Xiao et al., 2022; Reef et al., 2019). Nutrient dynamics in arid soils (N < 0.05%; Almahasheer et al., 2016) pose additional challenges, with NPK fertilization (50 g N, 25 g P, 20 g K m⁻²) increasing biomass by 35–60% (Osman and AboHassan, 2010; Miah and Moula, 2019), although excessive inputs (200 g N m⁻²) risk a 40% survival reduction due to toxicity (Lovelock et al., 2009). Restoration strategies show varied efficacy: Artificial soil elevation (20–30 cm) enhances survival to 70% by improving aeration (+150 mV soil redox potential; Corona-Salto et al., 2024), nursery pre-growth yields 44–70% survival (Alrubaye et al., 2023), salvage replanting achieves 82% survival for mature trees (Erftemeijer et al., 2021), and blended seawater irrigation (15–25 PSU) boosts germination to 85% (Lebda et al., 2024). Hydrological interventions, such as the fishbone technique’s tidal channels, reduce salinity stress and enhance recruitment (Primavera et al., 2011; The Indian Express, 2022; Indian Masterminds, 2023). Sabkha environments, however, present extreme challenges, with salinity levels reaching ~239 ppt (157.2‰ Cl⁻, 78.8‰ Na⁺), EC at 20,800 μS/cm, acidic pH (6.9), and H₂S toxicity from algal decomposition, reducing survival to below 20% and growth by 20–30%, necessitating targeted interventions such as salinity dilution, pH buffering, and aeration (Al-Mhaidib, 2003; Chang et al., 2020). A. marina’s carbon sequestration potential (28–45 Mg C ha⁻¹; Shaltout et al., 2021) underscores its value for coastal protection and climate mitigation, yet practical and research challenges persist. Financial constraints are significant, with artificial elevation costing $25,000–$50,000 ha⁻¹, irrigation infrastructure ranging from $10,000 to $50,000 ha⁻¹ initially ($2,000–$5,000 ha⁻¹ annually), and NPK fertilization requiring $1,500 ha⁻¹ per application plus $500–$1,000 ha⁻¹ for soil monitoring (Lewis and Brown, 2014; Erftemeijer et al., 2020). Logistical hurdles, including sediment transport, freshwater scarcity, and managing runoff to prevent eutrophication, limit scalability (Kathiresan and Bingham, 2001), while industrial pollutants (e.g., 45 mg kg⁻¹ Pb in Bahrain) pose phytotoxicity risks, necessitating pre-planting sediment testing (Abou Seedo et al., 2017). Research gaps include limited long-term field trials in hypersaline regions, insufficient data on organic amendments such as biochar (Guo et al., 2018), and standardized carbon certification protocols. Climate change exacerbates these issues, with sea-level rise (1–3.7 mm yr.⁻¹; Intergovernmental Panel on Climate Change, 2021) increasing submergence stress and rising temperatures (e.g., 40°C in Kuwait) intensifying salinity stress (Chang et al., 2020). Sustainable solutions include localized nutrient recycling (e.g., fish waste, $500 ha⁻¹), cost-effective tidal channels ($5,000–$15,000 ha⁻¹), and community-driven models to reduce labor costs (Erftemeijer et al., 2020). Carbon offsetting, leveraging A. marina’s sequestration capacity (3–5 t CO₂e ha⁻¹ yr.⁻¹), offers financial returns ($5–$50 per t CO₂e), potentially offsetting costs ($2,000 ha⁻¹ over 20 years) through hybrid financing models such as grants and ecosystem service payments (Al-Guwaiz et al., 2021). Future research should prioritize multi-year trials, climate resilience monitoring, and the integration of sabkha-specific strategies to ensure the long-term ecological and economic sustainability of A. marina restoration in arid coastal ecosystems (Table 5).

The synthesis of 55 studies on Avicennia marina (Forssk.) Vierh. restoration in arid, hypersaline coastal regions reveals significant methodological heterogeneity, encompassing study design, duration, spatial scale, environmental conditions, and outcome metrics, which collectively challenge the comparability and generalizability of findings. Study designs vary widely, from controlled greenhouse experiments (e.g., Santos et al., 2021; Naidoo, 1987) with small sample sizes (30–50 seedlings) and controlled salinity (0–40 ppt) to large-scale field trials (e.g., Erftemeijer et al., 2020; Alrubaye et al., 2023) spanning 5–17 ha under natural tidal gradients (15–48 ppt) and observational case studies (e.g., Mousavi et al., 2024) in natural settings. Controlled experiments provide precise physiological insights—such as 85% germination at 15 ppt (Lebda et al., 2024)—but often overestimate survival compared to field conditions, where industrial stressors reduce rates to 44% (Alrubaye et al., 2023). Field studies, while ecologically relevant, vary in scale and replication, complicating meta-analysis: Erftemeijer et al. (2020) reported 26% survival over 30 years across 16.5 ha, whereas Corona-Salto et al. (2024) achieved 70% survival in 18 months across 60 m². Study durations further exacerbate heterogeneity, with short-term studies (e.g., 6 months; Miah and Moula, 2019) reporting higher survival (60–85%; Bhat et al., 2004) and growth (173.3 cm height; Alrubaye et al., 2023), contrasted by long-term studies (e.g., 30 years; Erftemeijer et al., 2020) showing declining survival (26%) due to cumulative stressors such as hypersalinity and pollution. Environmental variability across arid regions (e.g., Persian Gulf, Red Sea, and Australia) introduces additional complexity, with salinity (15–60 ppt), rainfall (<50–2,000 mm), and soil types (sandy vs. clay-rich) influencing outcomes—nutrient-rich soils in Qatar support 41.44 Mg ha⁻¹ biomass (Chang et al., 2020), while polluted soils in Al Jubail cause 50% canopy loss (Ali et al., 2009). Sabkha environments further complicate synthesis, with extreme salinity (~239 ppt), EC (20,800 μS/cm), acidic pH (6.9), and H₂S toxicity reducing survival to below 20% and growth by 20–30%, far exceeding typical study conditions (Al-Mhaidib, 2003; Chang et al., 2020). Diverse outcome metrics—survival rates (18–85%), biomass (15.9–44.91 Mg ha⁻¹), height (25 cm–5 m), and carbon storage (18.2–78 Mg C ha⁻¹)—hinder quantitative synthesis as variations in technique, site conditions, and stand age obscure regional comparisons. Aggregated estimates (70–80% survival, 28–45 Mg C ha⁻¹ carbon storage) risk overemphasizing short-term, small-scale successes and overgeneralizing across heterogeneous environments, necessitating region-specific analyses. To address this, future studies should adopt standardized protocols per SER guidelines, reporting consistent metrics (e.g., % survival at 2, 5, and 10 years; biomass in Mg ha⁻¹). Prioritizing long-term field trials (>5 years) and quantitative meta-analyses weighted by study rigor, sample size, and duration will enhance synthesis accuracy, ensuring robust conclusions for A. marina restoration in hypersaline arid regions.

Mangrove ecosystems, crucial for coastal resilience, carbon sequestration, and biodiversity conservation, face escalating threats from climate change, deforestation, and unsustainable practices, yet the integration of traditional ecological knowledge (TEK), local ecological knowledge (LEK), and scientific ecological knowledge (SEK) offers a synergistic framework for sustainable Avicennia marina restoration in hypersaline arid regions (Berkes, 2008; Berkes, 2012). TEK and LEK, rooted in indigenous and community-based stewardship, provide context-specific insights into site selection, species choice, planting techniques, and participatory monitoring, while SEK contributes rigorous empirical methodologies and scalable frameworks to enhance restoration efficacy (Berkes, 2008; Berkes, 2012; Ravaoarinorotsihoarana et al., 2023; Marquez and Olavides, 2024). In Madagascar’s Velondriake region, fishers’ TEK on tidal patterns and salinity gradients guided A. marina site selection, achieving 82.5% survival over 3 years by targeting sites with optimal inundation (<50 cm) and salinity (15–30 ppt), while women’s groups using traditional 1-m propagule spacing restored 50 ha, boosting fish stocks and generating $500–$1,000 ha⁻¹ annually through ecotourism, with community-led monitoring reducing costs by 30% (Ravaoarinorotsihoarana et al., 2023). In the Philippines Banacon Island, TEK-informed fishbone tidal channels mitigated salinity stress, yielding 70% survival over 5 years for Rhizophora and Avicennia species, increasing crab yields by 40% and household incomes by 15% ($200–$300 yr.⁻¹) at 20% lower costs than mechanized dredging (Marquez and Olavides, 2024). In Tanzania’s Rufiji Delta, women’s TEK on seasonal rainfall optimized wet-season planting, achieving 65% survival over 2 years, supporting shrimp fisheries, and raising incomes by 10% ($100–$150 yr.⁻¹) with 25% cost savings through community monitoring (Sabai and Sisitka, 2013). TEK-derived buried clay pot irrigation offers water efficiency but faces challenges with inconsistent flow in saturated soils, requiring optimized designs (Vasudevan et al., 2011). Sabkha environments, with salinity (~239 ppt), EC (20,800 μS/cm), and H₂S toxicity, reduce survival to below 20%, necessitating TEK-informed strategies such as Bedouin knowledge of salinity-tolerant planting zones combined with SEK-based aeration and pH buffering (Al-Mhaidib, 2003; Chang et al., 2020) (Table 6). Challenges to broader adoption include limited TEK documentation in arid regions, cultural erosion, land tenure conflicts, and funding constraints (Casimirri, 2003; Stori et al., 2019; Nguyen et al., 2016). Proposed solutions include establishing TEK repositories through community-led workshops, funding TEK-SEK training for 1,000 practitioners by 2030 under the Saudi Green Initiative (SGI) and Middle East Green Initiative (MGI), and developing standardized protocols for participatory monitoring and equitable benefit sharing. Innovative financing, such as Payment for Ecosystem Services, can offset costs and ensure sustainability (Boromthanarat et al., 2006; Haq et al., 2023). Future research should prioritize standardized TEK-SEK protocols, community-led documentation, robust monitoring of ecological (e.g., survival and carbon sequestration) and socioeconomic (e.g., income gains) outcomes, and policy innovation to address cultural erosion and data gaps, ensuring A. marina restoration aligns with global sustainability goals such as the UN Decade on Ecosystem Restoration.

Carbon offsetting, leveraging Avicennia marina sequestration capacity (28–45 Mg C ha⁻¹, equivalent to 103–165 t CO₂e ha⁻¹; Shaltout et al., 2021), is increasingly proposed as a potential financial mechanism to support mangrove restoration in hypersaline arid regions, yet its economic feasibility remains untested due to the absence of comprehensive cost analyses and cost–benefit assessments in existing case studies. This proposed framework outlines a structured approach to evaluate carbon offsetting potential, focusing on carbon sequestration quantification, market alignment, economic considerations, and community integration, tailored to arid coastal systems and aligned with the Saudi Green Initiative (SGI) and Middle East Green Initiative (MGI) goals. Quantifying carbon sequestration requires standardized methodologies, such as allometric equations for above-ground biomass (AGB) and below-ground biomass (BGB), and soil core sampling to 1 m depth, with baseline inventories pre-restoration and annual monitoring over 5–20 years. Regional studies report carbon stocks of 78 Mg C ha⁻¹ in Abu Dhabi (Alsumaiti and Shahid, 2019) and 28.9 Mg C ha⁻¹ in Jazan, Saudi Arabia (1,350 trees ha⁻¹; Shaltout et al., 2021), with annual sequestration rates of 3–5 t CO₂e ha⁻¹ yr.⁻¹ (Al-Guwaiz et al., 2021). Sabkha environments, however, with salinity levels reaching ~239 ppt, EC at 20,800 μS/cm, acidic pH (6.9), and H₂S toxicity, may reduce carbon sequestration potential by limiting growth and survival to below 20% (Al-Mhaidib, 2003; Chang et al., 2020), necessitating site-specific adjustments in arid regions. Market alignment involves adhering to international carbon standards (e.g., Verified Carbon Standard [VCS] and Gold Standard) to access voluntary and compliance markets, such as Saudi Arabia’s Regional Voluntary Carbon Market, while considering co-benefits such as biodiversity and coastal protection, which may enhance mangrove credit values (Al-Guwaiz et al., 2021). Economic feasibility assessments are critical but currently lacking as restoration costs (e.g., tidal channels: $5,000–$15,000 ha⁻¹; irrigation: $10,000–$50,000 ha⁻¹; Lewis and Brown, 2014) and maintenance expenses ($2,000–$5,000 ha⁻¹ yr.⁻¹) have not been systematically weighed against potential carbon revenues or ecosystem service benefits (e.g., fishery yields; Ravaoarinorotsihoarana et al., 2023). Community integration, as demonstrated in Madagascar, can enhance project sustainability through equitable benefit sharing and reduced labor costs (Erftemeijer et al., 2020) but requires formal mechanisms to ensure long-term engagement. The lack of cost–benefit data underscores the preliminary nature of carbon offsetting proposals for A. marina restoration, highlighting the need for future research to validate sequestration rates in restored stands (5–15 years), develop regional carbon pricing models incorporating co-benefits, and conduct pilot projects to assess economic viability under SGI and MGI frameworks. Addressing sabkha-specific challenges through salinity dilution and pH buffering will also be essential to ensure feasibility in the most extreme arid environments.

Restoration of Avicennia marina in hypersaline arid regions is crucial for enhancing coastal resilience, supporting biodiversity, and advancing carbon sequestration, yet high costs and logistical complexities of strategies such as NPK fertilization, artificial soil elevation, and blended seawater irrigation underscore the need for innovative and scalable solutions. A synthesis of 50 studies demonstrates that optimized hydrological management (e.g., 20–30 cm elevation), controlled NPK fertilization, nursery pre-growth, and salvage replanting can achieve 70–80% survival within 2–3 years, yielding 40 Mg ha⁻¹ biomass and 28–45 Mg C ha⁻¹ in carbon storage, and provided risks such as nutrient overload and heavy metal contamination are mitigated (Al-Guwaiz et al., 2021; Lewis and Brown, 2014). Sabkha environments, with extreme salinity (~239 ppt), EC (20,800 μS/cm), acidic pH (6.9), and H₂S toxicity, reduce survival to below 20% and growth by 20–30%, necessitating targeted interventions such as salinity dilution, pH buffering, and aeration (Al-Mhaidib, 2003; Chang et al., 2020). Carbon offsetting, leveraging mangroves’ sequestration capacity (3–5 t CO₂e ha⁻¹ yr.⁻¹), is increasingly proposed as a potential funding mechanism, but its economic feasibility remains untested due to the absence of comprehensive cost–benefit assessments in current case studies (Al-Guwaiz et al., 2021). Context-specific innovations, such as localized nutrient recycling (e.g., biochar, ~$500 ha⁻¹), hydrological modifications ($5,000–$15,000 ha⁻¹), and community-driven efforts, can minimize reliance on costly inputs, while salt-tolerant cultivars and low-cost pollution assessments ($500 ha⁻¹) address hypersaline and industrial challenges (Erftemeijer et al., 2020). Future research should prioritize multi-year field trials to validate organic amendments, long-term monitoring to assess climate resilience, and pilot projects to evaluate the economic viability of carbon offset programs under frameworks such as the Saudi Green Initiative (SGI) and Middle East Green Initiative (MGI). These evidence-based, adaptable strategies, tailored to address sabkha-specific constraints, can globally enhance coastal resilience and carbon sequestration in hypersaline arid regions, urging policymakers to integrate A. marina restoration into broader environmental sustainability initiatives.