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Thematic focus: Ecosystem management, Environmental governance, Resource efficiency
Sand, rarer than one thinks
Sand and gravel are mined world-wide and account for the largest volume of solid material extracted globally. Formed by erosive processes over thousands of years (John, 2009), they are now being extracted at a rate far greater than their renewal. Furthermore, the volume being extracted is having a major impact on rivers, deltas and coastal and marine ecosystems (Figure 1), results in loss of land through river or coastal erosion, lowering of the water table and decreases in the amount of sediment supply. Despite the colossal quantities of sand and gravel being used, our increasing dependence on them and the significant impact that their extraction has on the environment, this issue has been mostly ignored by policy makers and remains largely unknown by the general public.
Why is this issue important?
Globally, between 47 and 59 billion tonnes of material is mined every year (Steinberger et al., 2010), of which sand and gravel, hereafter known as aggregates, account for both the largest share (from 68% to 85%) and the fastest extraction increase (Krausmann et al., 2009). Surprisingly, although more sand and gravel are mined than any other material, reliable data on their extraction in certain developed countries are available only for recent years (Krausmann et al., 2009). The absence of global data on aggregates mining makes environmental assessment very difficult and has contributed to the lack of awareness about this issue.
One way to estimate the global use of aggregates indirectly is through the production of cement for concrete (concrete is made with cement, water, sand and gravel). The production of cement is reported by 150 countries and reached 3.7 billion tonnes in 2012 (USGS, 2013a). For each tonne of cement, the building industry needs about six to seven times more tonnes of sand and gravel (USGS, 2013b). Thus, the world’s use of aggregates for concrete can be estimated at 25.9 billion to 29.6 billion tonnes a year for 2012 alone. This represents enough concrete to build a wall 27 metres high by 27 metres wide around the equator.
Added to this are all the aggregates used in land reclamation, shoreline developments and road embankments (for which the global statistics are unavailable), plus the 180 million tonnes of sand used in industry (USGS, 2012). Aggregates also contribute to 90% of asphalt pavements and 80% of concrete roads (Robinson and Brown, 2002). China alone built 146,400 kilometres of road in one year (EDE, 2013) — an indication of the world demand for aggregates.
Figure 1: Beach sand mining in Sierra Leone.
Taking all these estimates into account, a conservative estimate for the world consumption of aggregates exceeds 40 billion tonnes a year. This is twice the yearly amount of sediment carried by all of the rivers of the world (Milliman and Syvitski, 1992), making humankind the largest of the planet’s transforming agent with respect to aggregates (Radford, 2005).
This large quantity of material cannot be extracted (Figure 1) and used without a significant impact on the environment (Sonak et al., 2006, Kondolf, 1994). Extraction has an impact on biodiversity, water turbidity, water table levels and landscape (Table 1) and on climate through carbon dioxide emissions from transportation. There are also socio-economic, cultural and even political consequences. In some extreme cases, the mining of marine aggregates has changed international boundaries, such as through the disappearance of sand islands in Indonesia (New York Times, 2010; Guerin, 2003).
Table 1:Summary of the main consequences of extraction of aggregates.
What are the findings?
The demand for aggregates stems from a wide range of sectors, including production of glass, electronics and aeronautics. However, its largest use is in construction (see example on Dubai in Box 1) and land reclamation (see example on Singapore in Box 2). The trend for aggregates extraction can be estimated using cement production as a proxy. This has multiplied three-fold in the last 20 years from 1.37 billion tonnes of cement in 1994 to 3.7 billion tonnes in 2012 (USGS, 2013a) mainly as a result of rapid economic growth in Asia (UNEP and CSIRO, 2011), and spurred by China’s development, which in 2012 absorbed 58% of the world cement production, or 2.15 billion tonnes (Figure 2). Five countries — China (58%), India (6.75%), the United States (2%), Brazil and Turkey — produce 70% of the world’s cement (USGS, 2013c). However, cement demand by China has increased exponentially by 437.5% in 20 years, while use in the rest of the world increased by 59.8% (Figure 2). Each Chinese citizen is currently using 6.6 times more cement than a U.S. citizen (USGS, 2013a). Demand continues to increase with new infrastructure and renewal of existing infrastructure (roads, bridges, dams, houses) — all dependent on the availability of aggregates.
Sand was until recently extracted in land quarries and riverbeds; however, a shift to marine and coastal aggregates mining has occurred due to the decline of inland resources. River and marine aggregates remain the main sources for building and land reclamation. For concrete, in-stream gravel requires less processing and produces high-quality material (Kondolf, 1997), while marine aggregate needs to be thoroughly washed to remove salt. If the sodium is not removed from marine aggregate, a structure built with it might collapse after few decades due to corrosion of its metal structures (Delestrac, 2013). Most sand from deserts cannot be used for concrete and land reclaiming, as the wind erosion process forms round grains that do not bind well (Zhang et al., 2006).
Figure 2: Left: Cement production from 1994 to 2012 in billion metric tonnes. Sources: Emissions of CO2 - from Cement Production (CDIAC) as in UNEP Environment Data Explorer (EDE, 2014). Right: Emissions of carbon dioxide from cement production in China.
Impact on the environment
In developing countries, mining and dredging regulations are often established without scientific understanding of the consequences, and projects are carried out without environmental impact assessments (Maya et al., 2012; Saviour, 2012). As a result, aggregate mining has affected the provision, protection and regulation of ecosystem services.
Impact on marine biodiversity
The mining of marine aggregates is increasing significantly. Although the consequences of substrate mining are hidden, they are tremendous (Figure 3). Marine sand mining has had an impact on seabed flora and fauna (Krause et al., 2010). Dredging and extraction of aggregates from the benthic (sea bottom) zone destroys organisms, habitats and ecosystems and deeply affects the composition of biodiversity, usually leading to a net decline in faunal biomass and abundance (Desprez et al., 2010) or a shift in species composition. Long-term recovery can occur only where original sediment composition is being restored (Boyd et al., 2005).
Aggregate particles that are too fine to be used are rejected by dredging boats, releasing vast dust plumes and changing water turbidity, resulting in major changes to aquatic and riparian (i.e. river banks) habitats over large areas (Ashraf et al., 2011).
Figure 3: Direct and indirect consequences of aggregates dredging on the marine environment. Graph adapted from Tillin
Impact on inland biodiversity and rivers
Figure 4: River sand mining in India.
The mining of aggregates in rivers (Figure 4) has led to severe damage to river basins (Sreebha and Padmalal, 2011), including pollution and changes in levels of pH (Saviour, 2012). Removing sediment from rivers causes the river to cut its channel through the bed of the valley floor (or channel incision) both upstream and downstream of the extraction site. This leads to coarsening of bed material and lateral channel instability. It can change the riverbed itself (Kondolf, 1997). The removal of more than 12 million tonnes of sand a year from the Vembanad Lake catchment in India has led to the lowering of the riverbed by 7 to 15 centimetres a year (Padmalal et al., 2008). Incision can also cause the alluvial aquifer to drain to a lower level, resulting in a loss of aquifer storage (Kondolf, 1997). It can also increase flood frequency and intensity by reducing flood regulation capacity. However, lowering the water table is most threatening to water supply (Myers et al., 2000) exacerbating drought occurrence and severity as tributaries of major rivers dry up when sand mining reaches certain thresholds (John, 2009).
Coastal and inland erosion
Figure 5:Completed in 1990 at a cost of US$ 70 million, a tetrapod wall was constructed to prevent coastal erosion along the edges of the Male in the Maldives.
Erosion occurs largely from direct sand removal from beaches, mostly through illegal sand mining. It can also occur indirectly, as a result of near-shore marine dredging of aggregates, or as a result of sand mining in rivers (Kondolf, 1997). Damming and mining have reduced sediment delivery from rivers to many coastal areas, leading to accelerated beach erosion (Kondolf, 1997). Onshore sand mining in coastal dune systems such as those in Monterey Bay, California, in the United States, can also lead to long-term erosion, in this instance, 0.5 to 1.5 metres a year (Thornton et al., 2006).
By 2100, global average sea level rise is expected to reach 0.26 to 0.55 metres under the best-case scenario (of 70% reduction of greenhouse gas emissions), and nearly one metre under unabated increase in greenhouse gas emissions (IPCC, 2013a). This problem is particularly acute for small islands states, where retreat options are limited. In the Maldives, a few of the largest and highest islands, such as the capital city, Male, are being consolidated to ensure they can host the population displaced from low-lying islands (Figure 5). To strengthen the city, a large amount of sand is being imported to Male, to be used in building higher towers and coastal protection. The sand is taken from offshore sand islands. Paradoxically, the sands extracted for the protection measures in Male are leading to the lowering of some islands, increasing the need to relocate their populations (Delestrac, 2013).
Lake Poyang, the largest freshwater lake in China, is a distinctive site for biodiversity of international importance, including a Ramsar Wetland. It is also the largest source of sand in China (De Leeuw et al., 2010) and, with a conservative estimate of 236 million cubic metres a year of sand extraction, may be the largest sand extraction site in the world. By comparison, the three largest sand extraction sites in the United States combined represent 16 million cubic metres a year (De Leeuw et al., 2010). Sand mining has led to deepening and widening of the Lake Poyang channel and an increase in water discharge into the Yangtze River. This may have influenced the lowering of the lake’s water levels, which reached a historically low level in 2008 (De Leeuw et al., 2010).
Impact on climate
The transport of large quantity of aggregates, sometimes over long distances, has a direct impact on greenhouse gas emissions. The indirect impacts of aggregate mining come from the production of cement. For each tonne of cement, an average of 0.9 tonnes of carbon dioxide are produced (Mahasenan et al., 2003; USGS, 2012) . The Carbon Dioxide Information Analysis Center (CDIAC) estimates that 1.65 billion tonnes of carbon dioxide emissions were from cement production in 2010 alone, or nearly 5% of total greenhouse gas emissions (EDE, 2014). Total carbon emissions from cement amount to eight billion tonnes of carbon (equivalent of 29.3 billion tonnes of carbon dioxide) (IPCC, 2013b, p. 474) and has increased from 3% in the 1990s to 4% of greenhouse gas emissions from 2000 to 2009 (IPCC, 2013b, p.489).
Aggregates are, in most cases, a free resource, but their extraction comes at the expenses of other economic sectors and local livelihoods. Tourism may be affected through beach erosion (Kondolf, 1997), while fishing — both traditional and commercial — can be affected through destruction of benthic fauna (Cooper, 2013; Desprez et al., 2010). Agriculture could be affected through loss of agricultural land from river erosion (John, 2009) and the lowering of the water table (Kondolf, 1997). The insurance sector is affected through exacerbation of the impact of extreme events such as floods (Kondolf, 1997), droughts (John, 2009) and storm surges through decreased protection of beach fronts (Thornton et al., 2006). The erosion of coastal areas and beaches affects houses and infrastructure (Thornton et al., 2006; John, 2009). A decrease in bed load or channel shortening can cause downstream erosion including bank erosion and the undercutting or undermining of engineering structures such as bridges, side protection walls and structures for water supply (John, 2009; Padmalal et al., 2008).
A lack of proper scientific methodology for river sand mining has led to indiscriminate sand mining (John, 2009), while weak governance and corruption have led to widespread illegal mining (Saviour, 2012; Ashraf et al., 2011). Sand trading is a lucrative business, and there is evidence of illegal trading such as the case of the influential mafias in India (Ghosh, 2012).
In Morocco, half of the sand – 10 million cubic metres a year – comes from illegal coastal sand mining (Au fait, 2011). Sand smugglers have transformed a large beach into a rocky landscape between Safi and Essouira (l’Economiste, 2005; Khardijamal, 2011). Sand is often removed from beaches to build hotels, roads and other tourism-related infrastructure. In some locations, continued construction is likely to lead to an unsustainable situation and destruction of the main natural attraction for visitors — beaches themselves.
What are the implications for policy?
The lack of adequate information is limiting regulation of extraction in many developing countries (Sreebha and Padmalal, 2011). Access to data is difficult, and data are not standardised. There is limited collaboration/co-ordination between the marine scientific research establishments and the marine aggregates industry (Velegrakis et al., 2010). Except in the European Union, regulation efforts are few, especially in developing countries (Sreebha and Padmalal, 2011). Lack of monitoring systems, regulatory policies and environmental impact assessments have led to indiscriminate mining, triggering severe damage to the environment and related ecosystem services.
Reducing consumption of sand
One way to reduce consumption of sand is to optimise the use of existing buildings and infrastructure. Recycled building and quarry dust material can be a substitute for sand. Despite the very high value of minerals found in the sand, it is mostly used for concrete or is buried under highways. Concrete rubble should be recycled to avoid using aggregates, at least for low-quality uses (Kondolf, 1997). Recycling glass bottles would also reduce sand consumption.
Substitutes for sand are available. Khamput (2006) showed that quarry dust could be used to replace sand in general concrete structures. The replacement of sand by up to 40% of incinerator ash exhibits higher compressive strength than regular cement mortars (Al-Rawas et al., 2005). Some desert sand can be used if mixed with other material (Cisse et al., 2012; Zhang et al., 2006). There are alternatives for building houses, including wood, straw and recycled material. However, the current building industry is geared toward concrete know-how and equipment. Training of architects and engineers, new laws and regulations, and positive incentives are needed to initiate a shift for lowering our dependency on sand. Renewable and recycled materials need to be targeted for building houses and roads.
Tax on aggregates extraction to create incentives on alternatives
The current situation will continue unless sand extraction is correctly priced and taxed so that other options become economically viable. Despite the increasing rarity of sand, in the United States the price of sand has remained very stable, fluctuating from US$4.50 to US$6.7 a tonne between 1910 and 2013 (USGS, 2012) . Because sand is still very cheap – sand itself is freely accessible; only extraction costs need to be covered – there is little or no incentive to induce a change in our consumption.
Alternative sources of sand and gravel, which accumulate at the bottom of dams, can also be targeted. Their use would address the problem of these aggregates accumulating which leads to a reduced capacity of dams to store water and could result in the dams’ water intakes being blocked. Dams regularly release large amounts of water to flush out aggregates. Although currently more expensive, aggregates could be extracted from the dams.
Reducing the negative consequences of extraction
The environmental impact of in-stream mining might be avoided if the annual bed load were calculated and the mining of aggregates restricted to that value or less (Ashraf et al., 2011). Local environments should be studied to define the limits of acceptable changes (Cooper et al., 2011; Cooper, 2013).
Whilst it is critical for political leaders to take appropriate measures, the mining of aggregates has not yet reached their political agenda. This is primarily because sand loss has not yet reached a level of scarcity that would threaten the economy. Few, if any, measures are being implemented (See Box 3), with the notable exception of the European Union, and the United Kingdom in particular (Velegrakis et al., 2010; Tillin et al., 2011). There is a need for regulating sand extraction in both national and international waters. Experts recommend that large-scale mining, quarrying and reclamation activities should be authorized only after sound scientific assessment shows there would be limited impact on the environment (Maya et al., 2012). Other policy actions include the introduction of scientific mining operations, followed by ecological restoration. Greater consideration of substitute and sustainable use of the resource could drastically reduce impact on the environment (Chauhan, 2010).
Sand and gravel represent the highest volume of raw material used on earth after water. Their use greatly exceeds natural renewal rates. Moreover, the amount being mined is increasing exponentially, mainly as a result of rapid economic growth in Asia (UNEP and CSIRO, 2011). Negative effects on the environment are unequivocal and are occurring around the world. The problem is now so serious that the existence of river ecosystems is threatened in a number of locations (Kondolf, 1997; Sreebha and Padmalal, 2011). Damage is more severe in small river catchments. The same applies to threats to benthic ecosystems from marine extraction (Krause et al., 2010; Desprez et al., 2010; Boyd et al., 2005).
A large discrepancy exists between the magnitude of the problem and public awareness of it. The absence of global monitoring of aggregates extraction undoubtedly contributes to the gap in knowledge, which translates into a lack of action. As this issue is truly a major emerging one, there is a need for in-depth research. The implementation of a monitoring mechanism regarding global aggregate extractions and trade would shed light on the magnitude of this issue and bridge the current data and knowledge gap (Velegrakis et al., 2010). This would also raise this issue on the political agenda and perhaps lead to an international framework to improve extraction governance, as the current level of political concern clearly does not match the urgency of the situation.
Writer: Pascal Peduzzia
* The idea for this publication came from the film documentary "Le Sable: enquête sur une disparition," directed by Denis Delestrac and broadcast on Arte channel on May 28, 2013.
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