Seaports are among the most significant economic boosters for a nation internationally, regionally, and domestically. Numerous activities, including loading, unloading, storing, and transferring cargo between different transportation modes, result in several economic activities. Centripetal effects of these activities convert the ports into hubs for logistical and industrial activities, which have a domino effect by creating enhanced opportunities and, hence, economic growth. Efimova and Gapochka ^[1] showed that ports contribute to job creation significantly. They showed that for an increase of 1 million tonnes in turnover at the port of Antwerp of Belgium, the annual number of employees rose by 1285. Mehmood et al. ^[2] utilized an econometric analysis to prove that, during 2000–2019, 28 countries of the Organization for Economic Co-operation and Development (OECD) relied on their seaports for economic growth. Similarly, Ayesu et al. ^[3] provided clear evidence that seaport efficiency and trade enhanced the direct welfare outcomes of the people of Africa. Their study showed that increased seaport efficiency triggers positive effects on education, life expectancy, household consumption, and human development, with other positive momentums being multifold. However, the literature suggests that there are additional aspects of port development that need greater attention, especially the environment surrounding these seaports.

During port construction, a study undertaken by Palanques et al. ^[4] on the massive dumping of dredged material during and after the expansion of the last large port of Barcelona showed that the sediment dumping generated frequent (10–19 h per day), high (>203.2 mg/L), and short (50–90 min) suspended sediment concentration peaks. The unconsolidated sediment left after dumping was resuspended and advected, generating higher ambient suspended sediment concentrations (0.8–15.0 mg/L) than before the dumping (0.4–2.0 mg/L), which lasted for several days. This study highlights that seaports create noticeable environmental impacts during their construction and operations, both physically and biologically. If these environmental impacts remain uncontrolled, they may harm the surrounding terrestrial and marine ecosystems and jeopardize the wellbeing of coastal communities.

Once the port construction is completed, the ports continue to affect their surrounding environment. Žilinskas et al. ^[5] concluded that dredging of the entrance channel of the Klaipėda Port in Lithuania interrupted the alongshore sediment transport causing shore erosion on the updrift side of the port jetties. This was a result of the change in the wave field caused due to dredging, thereby altering the existing wave refraction pattern, changing the wave height regime, and eventually altering the sedimentation pattern ^[6]. The port structure in particular can alter the magnitude and direction of water currents differently, depending on the sizes and the permeability of the foundation structures used ^[7]. Ecologically, water stagnation can happen in certain locations within a port basin, inducing anoxic conditions, leading to low water quality, and killing marine animals ^[8]. Anton et al. ^[9], while analyzing the effects of breakwaters that emerged out of water, found that these breakwaters impact zoobenthos by destroying the habitats and benthic populations. In addition, due to reduced penetration of light and reduced oxygen due to sediment suspension, the quantity of phytoplankton was found to have been reduced.

With the known environmental impacts during and after the construction of seaports, it becomes imperative to consider the operations of seaports in a manner that would preserve the environment and ensure sustainability ^[10] to conform to the Sustainable Development Goals (SDG-2030) given by the United Nations. It is important to realize that increasing the gross domestic product (GDP) or boosting the national economy through the development of seaports without caring for the environment cannot provide sustainability ^[11]. While seaports are important for the economic growth and development of a nation, the oceanic environmental impacts that they cause are against the ethos of sustainability. This thus necessitates that nations and all stakeholders place greater emphasis on the possible negative impacts of ports’ construction and operation to ensure sustainability.

2. Understanding Ports, Port Activities, and Their Correlation with Human Sustenance

Seaports are maritime facilities driven by maritime trade that are created to provide access to the mainland from the seafront. Seaports are usually situated on the seafront or in estuaries, but they can also be found far inland, such as the port of Hamburg and the port of Manchester. The purpose of these ports is to act as entry and exit points for both men and materials during war and in peace. Accordingly, the ports perform the activities of loading, unloading, storage, and transportation of cargo and passengers, and they are considered to be extremely important to the global economy. These activities have an impact on world economics, as they support economic activities both at the port and in the hinterland, along with providing support systems of social and cultural functions by creating jobs and activities. The worldwide importance of ports has been discussed in detail by numerous researchers and needs no further deliberations here [12,13]^[12][13]. Over the years, as maritime trade has flourished, the ports have grown in terms of space occupied, technology used, and activities undertaken, resulting in greater job opportunities and ensuing overpopulation of port cities. This growing population has brought about a wide range of environmental impacts on local ecologies and waterways due to anthropogenic activities conducted on land and in the ocean ^[14], as shown in Figure 1. The most important of these impacts is the deterioration in water quality caused by dredging, oil spills, effluent discharge, and mindless disposal of solid and liquid pollutants ^[15]. In addition, activities such as construction and reclamation have created turbidity, changed siltation patterns, caused coastal erosion, impacted marine life due to noise and a lack of carbon sequestration due to ocean acidification, and impacted seaweed growth, to name but a few. Furthermore, activities of cargo handling, transportation, and emissions emanating from ships and industries have adversely impacted the quality of air in ports. Similarly, the impact of climate change has made port infrastructure particularly vulnerable to events such as rising sea levels, cyclones, coastal flooding, and increased precipitation ^[16]. In places where mangroves have been removed or destroyed to create access for ports, the impact on local marine life is grave and has impacted water quality, reduced the ability to withstand storm surges, and reduced habitats for commercial fishes and seafood ^[17]. The issue at hand has been compounded further, with modern ports tending to be multimodal hubs that escalate environmental deterioration due to greater demand for water frontage, regular dredging, prolonged usage of pilots, tugboats, and smaller vessels for transshipment using inland waterways, and trucks for hinterland transportation. While trade flourishes and the nation prospers through economic development, the environment is impacted adversely, resulting in both direct and indirect outcomes for human sustenance. With air, water, and land being polluted by port operations and activities, various social, institutional, operational, and land-use, conflicts arise ^[18]. Such conflicts arise because many gateway ports have become transit hubs and, hence, contribute little to the value chain but excessively to environmental deterioration. Accordingly, these ports are treated by the local population as foreign bodies rather than a driving force for socioeconomic development. Such skewed understanding causes conflict, wherein environmental impacts are disdained without giving due weightage to socioeconomic development. Such an approach impacts seaport governance and port efficiency to increase environmental impacts due to negligence and, hence, needs to be understood and resolved as early as possible. While regulatory bodies and legal authorities issue guidelines to control environmental impacts, these can be best considered as guidelines, since these bodies have limited enforcement powers. A case in point is the Environmental Protection Agency (EPA), which has issued several regulations regarding where low-emission engines can be manufactured, but cannot enforce the use of such equipment or control the hours of operation, resulting in continued high carbon emissions in ports ^[19]. Hence, it is important for the authorities to understand the risks and impacts, and to work towards preserving the environment and ensuring sustainability in line with SDG-2030. It is important to mention that even though the minor ports (especially those in the hinterland) are also considered equal if not greater contributors of pollutants, for this researticle wech the researchers limit ourthe discussion to seaports that are subjected to oceanic environmental impacts.

3. Seaports and Their Oceanic Environmental Impacts

One may notice that most of the changes are anthropogenic and have an oceanic impact on both physical and biological environmental aspects. To appreciate these changes better, and to understand the contribution of ports to these oceanic changes, wthe researchers will discuss the activities and the changes in greater detail. The environmental facets to be considered with respect to port development that create either physical impacts or biological impacts can be categorized into nine groups for ease of analysis, as shown in Figure 2 ^[20]. Each of these environmental facets has been discussed by several researchers and will not be deliberated here. Since doing justice to all of the environmental facets discussed in Figure 2 is not feasible in a single research article, wthe researchers will limit the discussion only to environmental facets emerging from the ocean.

3.1. Physical Seascape Alterations and Their Impacts

To protect the coastline and manmade structures on the coast, coastal protection structures have been used. However, these structures, which protrude above the ocean, occupy water space and, while providing the required protection, alter the hydrodynamic patterns of the sea waves and currents. This, in turn, alters the water current circulation, resulting in either strong currents or water stagnation. As documented in many studies, the innermost part of port basins often exhibits water stagnation. Cutroneo et al. ^[21] measured the bottom current within the Port of Genoa, Italy, and found that the current speed in the innermost part of the port was less than 0.05 m/s. Jeong et al. ^[22] numerically showed that the inner zone of the North Port of Incheon, South Korea, experienced very limited water circulation even during the period with steep hydraulic gradients when the tide was rising or falling. During stagnant water periods, the water was found to have degraded, with increased sediment. Saengsupavanich ^[8] presented a limited water circulation condition for the Chiang Saen Commercial Port of Thailand, which displayed unsatisfactory water quality within the port basin. When in the open sea near breakwaters, the water current is altered. The breakwater tends to increase the water current velocity at its tip and decreases it in its lee. Cutroneo et al. ^[21] showed that the current speed at the tip of the breakwater of the Port of Genoa, Italy, was much stronger than that inside the port basin. Rizwan et al. ^[23] found that the current speed around the tip of the Kutaraja Port, Indonesia, was very strong (greater than 0.4 m/s), while the current velocity in the breakwater-sheltered zone was less than 0.14 m/s. The increased water current velocity can pose risks to ships entering or leaving the port basins, or to small artisanal fishers navigating in the nearshore area. Like currents, wave patterns such as wave refraction and diffraction are also altered due to reclaimed areas and breakwaters in the port. Saengsupavanich et al. ^[24] revealed that, due to breakwaters, the wave height, water flow, and sediment movement get altered. Earlier, Ilic et al. ^[25] confirmed that the presence of breakwaters could transform waves, especially in shallow-water regions. Prukpitikul et al. ^[6] showed that a new proposed breakwater at the Sattahip Port, Thailand, changed the existing wave pattern around the port. Dredging, another necessary activity of most ports, changes seabed bathymetry. This results in altered wave regimes. Iouzzi et al. ^[26] numerically confirmed that the dredging of the navigation channel of the Mehdia Port, Morocco, led to an increase in wave height in and at the edges of the dredging area, as a result of a sudden increase in the water’s depth. The waves propagating across the excavation area refracted toward the areas of shallow water, resulting in increased wave height. Conversely, when the wave regimes (i.e., wave height and wave direction) change along the shoreline, coastline changes follow as a consequence of the modified alongshore sediment transport.

3.2. Biological Impacts

The oceans are considered to be rich in marine species. However, to date, only 240,000 species have been identified, with new ones being discovered on a near-daily basis [39]^[27]. It has been observed that the interface areas of the marine and terrestrial environments are the richest and the most productive with regard to marine life. These coastal regions act as nurseries for a number of species. If these coastal regions were to degrade, it would have a direct influence on the sustenance of the populations of the species that depend on these nurseries. In addition, vegetated coastal ecosystems such as mangroves, seagrass, plankton, seaweeds, and intertidal marshes, which sequester carbon in marine sediments, would also be impacted [40]^[28]. By converting natural coastlines into artificial ones through manmade structures such as ports, dykes, quays, etc., many of which have been built without ecological consideration, the natural habitats of these oceanic spaces are being destroyed. The resulting water contamination due to noise, construction, chemical, pollutants, oil, untreated human waste, and non-native species through ballast water or biofouling on the hulls of ships causes irreversible damage to the coastal ecosystem, affecting both animals and plants.

4. Existing Policies and Legal Provisions to Address These Pollutants

Since the factors influencing ports are well known, it is natural to assume that the process of quantification of the diffusion and transportation of pollutants in the ports is well established. One such method, the US EPA’s WASP4 model, helps analyze several pollutants in almost all water bodies [123]^[29]. When it comes to regulations, the maritime industry is an inherently reactive one that is slow to adopt disruptive and new technologies [124]^[30]. Accordingly, most of the regulations that exist in the maritime industry are a result of learning from an incident or a set of incidents. The International Convention for the Prevention of Pollution from Ships (MARPOL) [125]^[31], which aims to address tanker accidents and routine pollution through methods such as tank cleaning and the disposal of oily engine-room wastes, is an outcome of the Torrey Canyon disaster of 1967 [126]^[32]. As awareness of maritime pollution increased, long-term monitoring was utilized to refine the existing policies for ships [127]^[33] and port facilities through the development of various environmental performance indicators to measure environmental performance [128]^[34]. Similarly, various national, regional, and international regulations, guided by the IMO, aim to help achieve sustainability in the maritime industry. However, currently, the IMO guidelines are optional, and for a sustainable world they need to be made mandatory, along with strict enforcement. To encourage greater results, the efforts of those striving to achieve sustainability must be recognized, awarded, and encouraged. Similarly, those falling behind need to be educated and supported adequately with management solutions, finance for green technologies, and research and development. However, since whatever happens on the land has a direct impact on the oceans, this education needs to be holistic, addressing even those issues that are not directly connected to maritime shipping, such as plastic pollution [99]^[35], which need to be addressed to avoid the deterioration of our oceans. While several efforts, such as decarbonization by digitalization [129]^[36], the use of LNG as a decarbonizing fuel [130]^[37], the use of hydrogen as a decarbonizing fuel, and adopting the principles of a circular economy for the maritime industry [131]^[38], are considered to represent positive steps towards achieving the commitment of the IMO to achieving the targets of the Paris Agreement, there is a lot that needs to be done to achieve a net-zero emissions regime and towards the reception and treatment of ship-generated garbage. Similarly, issues regarding the reporting of ship collisions, ship damage due to piracy, and more need to be established and enforced. To safeguard species and habitats, Europe has a program named Natura 2000, which is the largest coordinated network for species and habitat protection and involves many European coasts and estuaries. Such regions should aim to restrict the discharge of scrubber wash water [46]^[39]. In this regard, the use of technology is on the rise, with AI and ML being used extensively to address the growing menace of plastic in the maritime space [132]^[40].