seafood in 2048. The scientists stated that the decline was a result of overfishing, pollution and other environmental factors that were reducing the population of fisheries at the same time as their ecosystems were being degraded. Yet again the analysis has met criticism as being fundamentally flawed, and many fishery management officials, industry representatives and scientists challenge the findings, although the debate continues. Many countries, such as Tonga, the United States, Australia and New Zealand, and international management bodies have taken steps to appropriately manage marine resources. The UN's Food and Agriculture Organization (FAO) released their biennial State of World Fisheries and Aquaculture in 2018 noting that capture fishery production has remained constant for the last two decades but unsustainable overfishing has increased to 33% of the world's fisheries. They also noted that aquaculture, the production of farmed fish, has increased from 120 million tonnes per year in 1990 to over 170 million tonnes in 2018. Populations of oceanic sharks and rays have been reduced by 71% since 1970, largely due to overfishing. More than three-quarters of the species comprising this group are now threatened with extinction. Irrigation The environmental impact of irrigation includes the changes in quantity and quality of soil and water as a result of irrigation and the ensuing effects on natural and social conditions at the tail-end and downstream of the irrigation scheme. The impacts stem from the changed hydrological conditions owing to the installation and operation of the scheme. An irrigation scheme often draws water from the river and distributes it over the irrigated area. As a hydrological result it is found that: the downstream river discharge is reduced the evaporation in the scheme is increased the groundwater recharge in the scheme is increased the level of the water table rises the drainage flow is increased. These may be called direct effects. Effects on soil and water quality are indirect and complex, and subsequent impacts on natural, ecological and socio-economic conditions are intricate. In some, but not all instances, water logging and soil salinization can result. However, irrigation can also be used, together with soil drainage, to overcome soil salinization by leaching excess salts from the vicinity of the root zone. Irrigation can also be done extracting groundwater by (tube)wells. As a hydrological result it is found that the level of the water descends. The effects may be water mining, land/soil subsidence, and, along the