Lifting heads up out of the sand

Chris Hackney

It is a fairly inconspicuous material. We probably pass it by without paying any particular attention to it. Yet, the humble grain of sand is perhaps the most important material in the development of human society. Without it we would not have concrete to construct buildings, glass for windows and drinking vessels and silicon chips to power the electronic revolution. It is even used in the manufacture of toothpaste and for filtering drinking water and wine (to fill your glasses).

We currently extract more sand than any other material aside from water. It is estimated our annual demand for this material is currently 50 billion tonnes. To put that in perspective, that is the equivalent of every person on the planet getting a gift of 18 kg of sand and gravel every day.  It is also twice the annual volume of sand supplied by the world’s rivers.

In order to meet our every growing demand, sand on the bed of river channels in deltas is being extracted at ever increasing rates. This is having detrimental effects on the environment, making river banks more unstable, resulting in the loss of land for agriculture and driving saline intrusion that is necessitating a change in agricultural crops to more saline tolerant varieties.

Perhaps the biggest challenge with managing the global sand resource is that of efficient monitoring to inform effective regulation. In many of the world’s large sandy rivers and deltas, river channels can be many kilometres wide, whilst sand extraction is occurring across hundreds of kilometres of river. It is just not physically possible to monitor this activity by eye on a regular basis. Recent work has, however, demonstrated that high-resolution satellite imagery can provide an effective monitoring tool.

Figure 1: A sand mining vessel and platform in operation on the Mekong River in Cambodia.

Using imagery provided by Planet Labs (PlanetScope) (see Figure 2),016 and tracked sand mining vessels in a reach of the Mekong River in Cambodia on a monthly basis. By generating heat maps of vessel activity we can show the reaches of the river that have experienced the greatest intensity of mining over the past five years, and how this intensity has changed and increased as demand for sand has grown. We are also then able to back out estimates of extracted volumes and find that these have increased year-on-year from around 26 Mt a year in 2016 to nearly 70 Mt a year in 2020 (by contrast the annual supply of sand from the Mekong is ~6 Mt a year!). This work was recently published in the journal Earth Surface Dynamics http://esurf.copernicus.org/preprints/esurf-2021-39/. We’ve now automated this processing utilising AI and image processing techniques and are applying it to the Mekong and Red River deltas in Vietnam, working with local institutions and regulatory bodies to operationalise this tool to ensure Vietnam can effectively regulate and monitor riverine sand mining in its two major delta environments.

Figure 2: Heat map depicting the density (boats per km2) of sand mining vessels on the Mekong River around Phnom Penh in Cambodia, overlain on satellite imagery from PlanetScope.

Given the dependence of society on sand and aggregates and its known environmental impacts, it is somewhat surprising that there is no mention of aggregate mining nor any consideration of its environmental costs and social effects in the UN Sustainable Development Goals (SDGs). In recently published work in One Earth Sand, gravel, and UN Sustainable Development Goals: Conflicts, synergies, and pathways forward: One Earth (cell.com) assess the synergies and conflicts between the SDGs and aggregate mining. We found major conflicts for eight SDGs, synergies for five SDGs, and neutral associations for four SDGs (see Figure 3).

These results show that conflicting interests can be seen directly and indirectly between goals intended to safeguard the environment and those promoting economic development, improving health, eliminating poverty, and reducing inequality.

Figure 3: Conflicts and synergies between aggregate usage and the UN Sustainable Development Goals. From Bendixen et al. (2021)

There is still lots of work to do to place this research within a local context that has relevance for global deltas. However, it is clear that if we are to ultimately define and move towards sustainable futures for deltas in SE Asia and around the world, then we need to incorporate the competing impacts of societal demand for sand and aggregate with its impacts on the environment and its interactions with the SDGs. Demand for sand is not going to disappear at the flick of a switch, it is so engrained in our way of life that it is just not possible to go ‘cold turkey’ with sand. We need alternative construction materials and ways to reduce our need for pristine sand – through reusing sand-based materials and modern designs that reduce dependence on concrete. But we also need to improve and increase monitoring and regulation to manage the environmental impact. Perhaps the most pressing issue is in defining what the safe operating spaces and thresholds for sediment extraction and starvation in deltas are before major tipping points in deltas socio-economic systems are reached and the sands of time really do run out.

Figure 4: Drone footage collected in Vietnam captures numerous blue sand mining ships collecting sand from the Mekong River. Credit: Southern Institute of Water Resources Research