The Global Programme of Action for the Protection of the Marine Environment from Land-Based Activities (GPA) is the only global intergovernmental mechanism directly addressing the connectivity between terrestrial, freshwater, coastal, and marine ecosystems. It was designed to address the accelerating degradation of the world’s oceans and coastal areas and aims to be a source of conceptual and practical guidance to be drawn upon by national and regional authorities for implementing sustained action to prevent, reduce, control, and eliminate marine degradation from land-based activities. The GPA focuses on three main source categories of land-based pollution, namely marine litter, nutrient, and wastewater pollution.
The continuous growth in the amount of solid waste that ends up in the environment and the slow rate of degradation of most items once in the ocean are together, leading to a gradual increase in marine litter found at sea, on the seafloor, and coastal shores. It has become an economic, environmental, human health, and aesthetic problem posing a complex and multi-dimensional challenge. In the global context, marine litter – especial marine plastic - has become a priority area.
More than 335 million tonnes of plastic were produced globally  in 2016, of which only a very small percentage is recycled. It is estimated that an average of 8 million tonnes of plastic finds its way into the world’s oceans each year, costing a minimum of USD 8 billion per year in environmental damage to marine ecosystems. This includes financial losses incurred by fisheries and tourism as well as time spent cleaning up beaches. The most significant downstream impact is on marine ecosystems. Once in the ocean, plastic does not go away: it fragments, eventually breaking down into small pieces known as microplastics, which may contain or sorb chemicals such as persistent organic pollutants that may be transferred into the food chain upon ingestion by marine organisms. Transported by ocean currents, few places around the globe have not been infested by this material.
The situation is likely to get worse unless there is improved management of solid waste and other land and marine-based sources and activities, including prevention, reduction, and control. Projections over the next 10 years show an increase in 40% of plastic production. Upstream action about production reduction and redesign of products is essential, which must be guided by life cycle analyses for targeted interventions.
There are growing concerns that the levels of reactive forms of nitrogen and phosphorus, collectively termed ‘nutrients,’ from excessive fertilizer and livestock waste runoff, wastewater and industrial emissions that leak to the environment are beyond the regenerative capacity of the earth’s ecosystems, notably freshwater ecosystems and the marine environment. This means that these ecosystems may no longer be able to absorb these nutrients without a severe, detrimental effect on ecosystem functioning and resilience. Phosphorus transport from agricultural land via rivers and the release of phosphorus-rich animal and human wastewater into the environment have degraded lakes, rivers, reservoirs, and coastal waters, causing considerable damages. In the case of nitrogen, a substantial amount of nitrogen entering agricultural soils, both by fertilization and biological fixation, is lost through surface run-off, leaching into groundwater and emissions in the atmosphere, according to the Our Nutrient World (2013) report . Nitrogen-based fertilizers are also the source of gaseous reactive nitrogen emissions. Globally, synthetic fertilizer and crops account for 12% of total ammonia emission, and FAO predictions indicate that global nitrous oxide (N2O) emissions from fertilizers will increase to between 35 and 60% by 2030.
One of the main impacts of nutrients is eutrophication, causing excessive plant growth and resulting in a depletion of oxygen in the water. Deoxygenation and hypoxia in coastal waters due to land-based nutrient pollution has increased exponentially since the 1960s and is estimated to cover an area of about 245,000 km2 worldwide (UN DOALOS, 2016)  with over 700 eutrophic and hypoxic coastal systems worldwide (Diaz et al., 2010). Major recent global events (e.g., GPA/IGR-3, Rio+20, etc.) have recognized the adverse impacts of misuse of nutrients and called for the development of strategies and policies to promote circular-economy approaches for sustainable use of nutrients, to realize economic benefits while sustaining the health of the oceans and coastal ecosystems. Our Nutrient World report notes that nutrient management represents a nexus that unites many global development issues. It presented the case for how improved management of nutrients would simultaneously make quantified contributions toward meeting existing global commitments for improving/protecting water, air, soil, climate, and biodiversity. At the same time, it could deliver consequent contributions to food and energy security with major net social and economic benefits.
Wastewater is commonly defined as a combination of domestic effluents such as blackwater – excreta, urine, and faecal sludge – and greywater – kitchen and bathing wastewater, as well as water from commercial establishments and institutions including hospitals. Industrial effluents, stormwater, and other urban run-offs, as well as agricultural, horticultural, and aquaculture effluents, are also considered wastewater. Wastewater is almost entirely composed of water (99 percent) and suspended, colloidal, and dissolved solids (1 percent). Untreated wastewater usually contains a large volume of waterborne pathogens that are harmful to human health and the environment. It also contains different nutrients including phosphorus, nitrogen, and potassium: while a certain amount of nutrients is helpful for the growth of aquatic plants, an excessive amount could favor algae bloom and the decay, thus paving the way for the birth of “dead zones” and lead to the depletion of oxygen in watercourses, with consequent negative effects for the environment. Also, an excess of nitrogen may have detrimental consequences on human health, especially in low and middle-income countries, where rural communities rely on local water bodies for drinking purposes. The excess of nitrate, the soluble form of nitrogen, found in high concentration in drinking water may cause various diseases, including infant methemoglobinemia, also known as the “blue baby syndrome,” which can be fatal (Scientific American, 2016).
Recent studies also acknowledge the increasing amount of emerging pollutants present in wastewater, including pharmaceuticals, personal care products, additives, and pesticides, and recognize the harm that these chemicals have on human health. Another major trend occurring is the increasing amount of microplastics found in wastewater that are subsequently released in the aquatic ecosystems. Wastewater is an important factor in the distribution of microplastics: between 80 percent and 90 percent of the plastic particles contained in wastewater, persist in the sludge (Science Daily, 2018). Therefore, microplastics can be found in the sludge used as fertilizers, as well as in the aquatic ecosystems after wastewater is discharged into the environment.
Coral reefs are particularly vulnerable to wastewater and nutrient pollution, which consequently threatens the health and well-being of hundreds of millions of people who depend on coral reef ecosystem services for nutrition, livelihoods, and a safe living environment. With the influences of ocean warming and coral bleaching impacts, wastewater pollution constitutes a significant threat that must be addressed with urgency.
As only 3 percent of all the water on our planet is freshwater, and just 1 percent is available for drinking purposes, it is paramount to maximize the use of wastewater and low-quality waters, particularly in water scarcity-prone areas. Wastewater is conventionally seen as a liability instead of a renewable resource in the hydrological cycle. However, once it is used, it can be reused again. If properly managed, wastewater can also help address other challenges, including water scarcity, groundwater recharge, biogas production, and the creation of green jobs. Managing sanitation and wastewater sustainably allows us to minimize the depletion of water resources, avoid environmental degradation, and protect human health.