What if I told you that one of the humblest and most ubiquitous of materials is potentially the Achilles heel for our entire urban development paradigm?

Sand is probably not something most people think of when they think of scarce resources with a large environmental footprint. But as a non-renewable resource where, economically viable supplies are diminishing rapidly, we need to stop taking it for granted.

The UNEP estimates that 50 billion tons of sand and gravel is used in construction and manufacturing every year – an amount sufficient to build a wall 27 metres wide and 27 metres high around the entire Earth every single year. And the scale of our consumption is expected to grow in coming years.

The only natural resource humans consume more of is water.

The non-renewable status of sand is probably not obvious to most people. From a geological perspective new sand is constantly being created, but it takes thousands of years for the forces of erosion and deposition to convert silica-rich rock to the kind of silica sand used for manufacturing glass and glazing, concrete and asphalt and other common products and materials.

For example, it takes 10 tonnes of sand to make one tonne of construction concrete. The average detached dwelling requires 14 tonnes of concrete – which means 140 tonnes of sand just for the concrete. Then there’s the silica sand used in the glazing, the shower screen glass, the light fixtures, mirrors, and so forth.

Multiply that by just one high rise and we are talking many kilotonnes of sand per floor.

Sand is everywhere – but not every sand is suitable

The scarcity of the resource is complicated by the fact only a specific type of sand that is high in silicone dioxide is suitable for most construction-related applications. This sand comes only from the weathering of quartz-bearing rocks found along coastlines and riverbeds. We can’t use basalt sand, and we can’t use sand that is high in clay sediments. And while there is an abundance of sand in desert dunes, because it is the result of aeolian (wind) erosion, it is too rough and fine for particles to be bound.

Coastal sand deposits from the weathering of quartz with rounded particles from the action of water are a major source of construction sand, and therein lies a problem. Coastal areas are also valuable for their amenity, as sites for established communities. The sand on our coastlines also plays an important role in protecting the shoreline from tidal impacts, including wave action and erosion.

River sands are also a source, but again, there is an environmental trade-off that is becoming increasingly untenable.

As the accessible and less contentious extraction sites in rivers, streams and the coastline are depleted, sand is sourced from deeper in the ocean or from more extensive dredging of river and stream sources. This has a major impact on the ecosystem, with consequences that trickle up through the web of ecosystem services and biodiversity that sustains us.

Sifting through possible solutions

The bottom line is we are part of one global environment; actions in one place have far-reaching impacts elsewhere. This is a way of thinking that is common among First Nations Peoples, perceiving humans and the environment as indivisible and being careful stewards of the resources from nature.

There are ways we can apply this thinking in considering the sand dilemma. We can start by assessing whether new materials are needed for every application.

Can we repurpose an existing building and retain the structural concrete and some or all the glazing? Can we specify an alternative to sand for some applications such as using recycled ‘glass sand’ for bedding pipework, road base or pathways as Lismore City Council has been trialling? Can we source glazing units that utilise recycled glass and recycled aluminium? Can we replace areas of hardstand pavement with a combination of living turf and reclaimed bricks for paving pathways?

If we start valuing construction sand as the scarce, non-renewable resource it is, we can make better decisions around using it only where no alternative material will do. As a result, we may even become inspired to design and deliver new and improved habitats for humans that do not compromise the habitats of other species as a consequence of their construction.

Biodiversity, ecology and other unpriced essentials

The fact sand has not generally been treated as a valuable part of the ecology is partly due to the challenges we have in attributing value to biodiversity, ecosystem services and landscapes generally.

When we look at an environmental impact assessment, for example, the business case struggles to put numbers that quantify the value of biodiversity. Even natural accounting models have not captured many aspects of the environmental function of sand.

Sand plays a key role in modulating river flows, filtering water and in helping break down large pieces of dead vegetation and other materials into finer silts and sediments. Where there is significant extraction, rivers can become both faster and wider, creating erosion issues and exacerbating flood risks.

It also provides important habitat for aquatic animals including crustaceans and worms that also clean up detritus and filter the water.  These animals are all a vital part of the intricate food web for other fauna including commercial fish species.

There is so much life under the water – but most of it is invisible in discussions about biodiversity protection.

I believe we need to apply the precautionary principle in considering the impact of our consumption of sand. We may not know where the sand in the concrete or glass we specify comes from, but we should consider it may be sourced from a jurisdiction with no or lax environmental protections where there are no limits of how much sand can be extracted.

Considering how urban development affects nature means looking off the plan to where our raw materials are coming from. We can design and build forest cities, but if their construction degrades nature elsewhere in the process, it is not truly sustainable.

By Erwin Ho, Sustainability Consultant, Cundall