Increasing invasion debt through good intentions: the risk and responsibilities of greening initiatives in the Middle East

1Alien invasive species pose a significant threat to biodiversity (Roy et al., 2023), particularly in arid desert environments, such as those in the Middle East, where alien species can have substantial ecological and economic repercussions. The arid desert ecosystem is highly adapted to extreme temperatures, low water availability, and nutrient-poor soils and is particularly vulnerable to the impacts of invasive species (Brooks, 2003;Underwood et al., 2019). These species often possess high reproductive capacity, rapid growth, and the ability to thrive under harsh conditions, enabling them to outcompete native flora and alter ecosystem functions (Gallardo et al., 2016;Milanović et al., 2020;Traveset & Richardson, 2006).Their proliferation is primarily driven by human activities, including deliberate introductions, cultivation, and accidental spread through global trade (Kueffer, 2017;van Kleunen et al., 2015). These invasions threaten biodiversity in urban areas and encroach upon agricultural lands and natural landscapes (Thomas et al., 2016). Invasive species reduce crop yields and increase agricultural land management costs (Alvarez & Solís, 2019), thereby altering water availability, soil fertility, and fire regimes in arid environments, which stresses native ecosystems. These species impact agricultural productivity and management costs, threatening food security and environmental stability, as they contribute to 60% of global animal and plant extinctions, with 16% being the sole driver (Roy et al., 2023).In parallel with the United Nations' Global Initiative on Reducing Land Degradation and Enhancing the Conservation of Terrestrial Habitats, and in response to climate challenges, the Middle East is increasingly focusing on environmental restoration and the development of green infrastructure (Alam & Azalie, 2023). The Middle East Green Initiative (MGI) and the Saudi Green Initiative (SGI), which aim to improve urban liveability and promote sustainable development (Abbass et al., 2018), were founded in 2021. The Middle East Green Initiative seeks to plant 50 billion trees region-wide, enhance regional cooperation to address climate change (Ghanem & Alamri, 2023), and initiate a transition to environmentally friendly economic activities, similar to the UAE's Green Agenda. While the MGI provides a framework, the Saudi Green Initiative ambitiously implements programs specifically designed to restore vegetation cover and reduce carbon emissions, aiming to generate 50% of the Kingdom's energy from renewable sources by 2030 and plant 10 billion trees (Khayat et al., 2023). Amongst other countries, Saudi Arabian landscapes are, therefore, at risk of being exposed to an increasing land management efforts, particularly afforestation that may increase the number of invasive plant species threatening the native biodiversity and the ecological integrity of these habitats (Alharthi, El-Sheikh, et al., 2023;Assaeed et al., 2021;Hassan et al., 2023). The increased risk of introducing and dispersing alien species through greening initiatives demands urgent attention. This raises a critical question: AreLarge-scale greening and restoration initiatives are promising, yet they also carry the unintended potential to introduce or spread invasive plants. Understanding both the risks embedded in such initiatives and the potential distribution dynamics of particular plants that could become invasive is crucial for anticipating and managing future ecological impacts.The Middle East Green Initiative (MGI) was established in 2021 as a multinational framework led by the Kingdom of Saudi Arabia (KSA) and endorsed by 25 countries (Middle East Green Initiative, 2024;Saudi and Middle East Green Initiatives, 2024). This comprehensive program operates through a structured governance system comprising 32 components that define the organisational structure, project submission protocols, evaluation criteria, and financing mechanisms. Saudi Green Initiative, as a sister initiative has launched 86 programs spanning afforestation, protected areas, agriculture, clean energy, climate action, policy, capacity and outreach, sport, tourism, urban greening and parks, waste and water management across 39 different private and public project owners (Albawardi et al., 2024;Saudi and Middle East Green Initiatives, 2024). A quarter of the announced programs are already underway, encompassing multiple strategic or site-based projects. During a recent steering meeting, the MGI announced plans to launch several qualifying projects in member countries by the end of 2025 (al-Abyad, 2024). Both initiatives have led to the establishment of governmental management entities focused on plant production, land management, wildlife conservation, and ecological restoration (e.g., the National Centres for Vegetation Cover, Wildlife, Environmental Compliance, as well as Greening UAE Initiative, and many others). Their launch has also led to an increase in public environmental awareness and support for urban greening and conservation (Khayat et al., 2023).Partially triggered by the MGI, seven states have released nationwide greening strategies, which are being implemented at regional and local levels through urban greening and natural restoration initiatives covering hundreds of thousands of square kilometres, with the target of planting billions of trees. In Saudi Arabia alone, seven urban greening initiatives are currently underway, comprising green infrastructure development, largescale recreational park developments, and the restoration of semi-natural environments. The number and amplitude of these greening initiatives have increased business opportunities in landscape and environmental planning, landscape contracting, and plant production (Fernando et al., 2019;Rahman et al., 2023;Shah et al., 2025;Swaffield et al., 2019), while associated capacity-building efforts can also drive biological invasions (Comte, 2024;Montaldi et al., 2024). In Saudi Arabia, for example, ongoing species trials aim to identify alien plants for their use in green infrastructure projects, supporting the Saudi Green Initiative (Alfarhan et al., 2021;Alharbi, 2024). These trials assess environmental suitability, resilience, growth rates, and usability in landscaping under local conditions (Alharthi, El-Sheikh, et al., 2023;Al-Sodany et al., 2016). Researchers and planners target plants that can thrive in urban areas while withstanding high temperatures, low water availability, and saline soils, thereby supporting greening efforts (Abbas et al., 2023;Alharthi, El-Shiekh, et al., 2023). Selected trials use acclimatised relocated plants to ensure successful growth when transplanted from controlled environments (Bruce et al., 2007).On another note, the highly adapted ecosystems of the Arabian Peninsula are severely understudied in the context of risk and impacts of invasive species on the local environment (Aljeddani et al., 2021;Thomas et al., 2016) threatening the productivity of cereal and fruit production. This impact may contribute to an increased reliance on food imports.To demonstrate the practical application of data-driven approaches in understanding species distribution patterns and underscore the risk of alien invasive plants, we conducted an exploratory analysis using species distribution modelling (SDM).We selected eight countries with a representative range of environmental conditions, from hyper-arid deserts to more temperate and mountainous climates. These countries also vary in size, biogeography, and data availability, allowing for a balanced assessment of species establishment potential. We modelled the potential distribution of 63 terrestrial invasive plant species using MAXENT (Elith et al., 2011), a presencepseudoabsence niche modelling algorithm, and predicted their distribution on the Arabian Peninsula. We compiled global occurrence records for the target species from GBIF (GBIF.org, 2024), eliminating duplicates, absence records, and entries with missing or erroneous locations, which resulted in 1,188,272 presence points. We further thinned the dataset to one occurrence per 1 km² grid cell to address spatial sampling bias.Environmental predictors included four soil parameters (bulk density, clay content, pH CaCl₂, and organic carbon) and five climatic variables (annual mean temperature, warmest month's maximum temperature, annual precipitation, precipitation of the warmest and coldest quarters) (Fick & Hijmans, 2017;Hageer et al., 2017;Hengl et al., 2017). For details see the SI.The results reveal the varying potential of unique species to inhabit and cover substantial portions of the surface area across the studied countries. 46 of the 63 assessed species have suitable habitats in 1% or more of the six countries. Yemen has the highest number of species ( 41), followed by Oman and Jordan (24) (Figure 2). More dramatically, 22 species could cover 10 % of the eight assessed countries. Yemen (15 species), Oman (6 species), and Jordan (9 species) remain the most suitable areas for these species. On a high level, these results demonstrate that more than 94% of species regulated in KSA may establish in any of the assessed countries. This preliminary investigation reveals the potential risks associated with invasive alien plants. It further confirms that data and technology are publicly available for data-driven policymaking and to support communication and outreach efforts to build public awareness.Arabia's ambitious afforestation and biodiversity goals have significantly boosted economic activity in the nursery and soil products sectors, driven by park, landscape, and nature park development projects. Horticulture, recognised as a significant pathway for introducing invasive alien plants (Reichard & White, 2001), is critical in this expansion. The Saudi landscaping and ornamental plants market is projected to grow at an annual rate of 8.1% (Techsciresearch, 2024), driven by urbanisation, rising disposable incomes, and supportive government policies for landscaping (6Wresearch, 2023). This growth is driven by Vision 2030 initiatives, alongside significant infrastructure and urban development projects in regional capitals such as Riyadh, Jeddah, and Dammam (Alharbi, 2024).However, before the surge in urban development and government programmes, millions of globally recognised invasive species were introduced in Saudi Arabia through greening and urbanisation projects (Al-Frayh et al., 1999). Limited data on failed introductions and establishment events highlight the risks of species trials and unintentional or accidental introductions becoming invasive. While Saudi Arabia's hyper-arid climate may suggest that globally impactful invasive species are unlikely to establish, the potential for their unintentional dispersal into more suitable regions with higher rainfall and temperate climates remains a significant concern.The tools and methods used in restoration and conservation initiatives can sometimes lead to unintended negative consequences. Across the Gulf, the prevention and control of invasive species primarily rely on plant To address marine vectors, GCC states are parties to the IMO Ballast Water ManagementConvention, which provides a defence against the spread of aquatic invasive species. At (unpublished data). This highlights the lack of awareness and the fact that they actively contribute to spreading invasive species. In summary, while recent regulatory efforts in Saudi Arabia demonstrate a commitment to addressing the risks associated with invasive species, significant challenges remain in enforcement and public awareness, particularly on a regional scale.To effectively bridge science with policy and planning, it is crucial to consider several factors to prevent the introduction, establishment, and spread of invasive species. We highlight the need for science-driven regulations that transcend administrative boundaries and are sufficiently nuanced to account for local environmental conditions.Similarly, enforcement efforts require a coordinated approach considering anthropogenic and natural dispersal pathways. Effective communication and outreach, along with fundamental advancements in regional research in biological invasion and agricultural science and technology, would further raise awareness.Traditionally, environmental regulations operate within administrative boundaries, overlooking ecological realities such as species dispersal and establishment (Török et al., 2018). Habitat-specific risk assessments are crucial for developing detailed species lists that enable policymakers to evaluate the likelihood of species establishment under specific climatic conditions (Marchioro & Krechemer, 2021;Vilizzi et al., 2021). For example, species struggling in hyper-arid environments may thrive in wetter regions, posing unforeseen risks to local ecosystems once dispersed. Furthermore, urban environments often represent climatic and edaphic combinations that do not exist in the natural environment and require regulatory efforts to consider ecological variables over administrative borders. Overarching species lists may not accurately reflect the dynamic nature of biological invasions, which can evolve rapidly in response to environmental changes and human alterations to the natural environment. Therefore, iterative policy review processes are required to create nuanced lists and regulations.Leveraging greening initiatives and the associated economic upswing can support the creation of standardised design and planting pallets and guidelines, urban greening codes, and species suitability lists that align with economic opportunities (Du & Zhang, 2020;Radhakrishnan et al., 2019;Threlfall et al., 2016).While species lists and design guidelines are commonly available for selected districts or projects (Balmford & Gaston, 1999;Tingstad et al., 2020), they often aim to advise species selection based on aesthetic and functional aspects of vegetation, ignoring the risk of adverse effects of plants, the combination of plants, and the transport of live plant material. Riyadh's authoritative planting guide (High Commission for the Development of Arriyadh, 2014), for example, includes five recently regulated invasive species without distinguishing native from alien or classifying invasiveness. Collaboration between regional governments and public actors in urban, environmental, and agricultural realms is necessary to establish robust assessment protocols for ornamental, farming, and soil products, ensuring a thorough evaluation of suitability and potential invasiveness. Those design and planning guides should not be the responsibility of commercial landscape planners and designers. Still, they should be based on science and data-driven tools authored and approved by qualified public entities.The movement of invasive plants from, to, and within Saudi Arabia is not solely a result of deliberate introductions but also stems from socio-economic activities and natural dispersal mechanisms. Anthropogenic drivers, including trade, tourism, and infrastructure development, contribute to the introduction and dispersal of species. The region's extensive road networks, shipping routes, and air travel hubs facilitate the accidental transport of propagules, while livestock movements, bird migrations, and marine currents contribute to natural dispersal.In addition to nuanced, ecosystem-specific species lists, introduction-dispersal risk assessment is a foundational tool for regulatory frameworks (Brenton-Rule et al., 2016;Essl et al., 2011), as well as for defining regulations and enforcement. Those spatially explicit assessments consider species traits, dispersal mechanisms, environmental suitability, and population demographics, as well as invasion contexts such as the intent of introduction and other anthropogenic factors.They also enable the early detection of emerging threats, such as "sleeper" species (Osunkoya et al., 2021) that remain dormant for years before proliferating under favourable conditions (Robeck et al., 2024). Moreover, risk assessments can facilitate targeted surveys and management, such as eradicating impactful species in sensitive natural environments and restricting high-risk species in landscaping projects while permitting controlled cultivation in less sensitive areas (e.g., urban).Effective policy responses must account for these diverse pathways, integrating socioeconomic data with ecological insights. For instance, predictive modelling can identify high-risk introduction routes and inform pre-emptive measures, such as enhanced biosecurity protocols at ports of entry and along transportation corridors. Such an integrated approach is vital for a region like Saudi Arabia, where human activity and natural processes often overlap, amplifying the risks of invasive species spread.Communication and collaboration are crucial for enhancing regulatory awareness among planners, growers, and the public (Smith et al., 2019). Actions should include equipping species lists with accessible identification keys and detailed descriptions to improve usability and encourage compliance. Leveraging greening initiatives can support the creation and standardisation of design guidelines, urban planning codes, and species suitability lists that align with economic opportunities (Coffey et al., 2020;Du & Zhang, collaboration is necessary to establish robust assessment protocols for ornamental, and species, their suitability and potential & et al., initiatives should address in local landscape planning to on managing invasive species local and enhancing the of invasive species addition to data-driven risk by the distribution identification tools can be further adapted to local and environmental and publicly available et al., 2021). 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