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Bringing sand to the beach

NASA’s Landsat satellite system has been used to gain accurate readings on the world’s sandy coastlines NASA’s Landsat satellite system has been used to gain accurate readings on the world’s sandy coastlines NASA Landsat
27 Aug
2018
The world’s first full global analysis of beaches reveals the state of each continent’s coastlines

Whether for essential access to the sea for fishing and transportation, protecting inland infrastructure from destructive oceanic storms, mining aggregate for concrete, or simply for recreation, beaches have multiple functions. But attempting to put an accurate number on what proportion of world’s coasts are composed of beaches has always been an immensely laborious and time-consuming process – let alone trying to calculate how this number may be changing through the years through erosion and accretion (the accumulation of material).

A two-month study utilising NASA’s Landsat satellites has for the first time made it possible to quantify the world’s beaches. The captured images were analysed by experts at Deltares, an independent research institute studying deltas, river basins and coasts, based in the Netherlands, whose software was taught to distinguish between sandy and/or grainy beaches, and alternative rocky shorelines. The results reveal that just shy of one-third of all ice-free shorelines are composed of beaches, with significant continental differences; two-thirds of African coasts are made up of beaches, in Europe this falls to a mere 22 per cent.

By comparing satellite imagery taken between 1984 and 2016, the results also reveal that 24 per cent of sandy beaches around the world are eroding (at a rate larger than 0.5m per year) and 27 per cent are growing, while the rest are stable. This means that, overall, the world’s beaches have slightly grown over the past three decades, although the trends reverse when it comes to beaches in marine protected areas, where 37 per cent of beaches are eroding, but only 32 per cent are accreting.

Australia and Africa are also both experiencing more erosion than growth, while Asia has experienced the largest accretion, partially due to human-led developments and land reclamations in countries such as China, Singapore, Bahrain and the UAE. ‘At this point we think the continental differences in beach erosion and accretion are largely influenced by human interventions along the coast,’ explains Arjen Luijendijk, a coastal development expert at Deltares. ‘Our next step will focus on distinguishing the human impact from the natural dynamics and trends.’

This was published in the September 2018 edition of Geographical magazine

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