From soil extraction new opportunities for agriculture

The production of building materials through soil negatively impacts the landscape but also opens up new possibilities for the development of climate and flood resilient agriculture. A lesson from Madagascar

by Matteo Cavallito

 

Soil extraction in urban and peri-urban contexts impacts the provision of ecosystem services by also reducing soil fertility and flood mitigation. But at the same time, it also appears to improve the ability to store water for use in irrigation, thereby contributing to food security and climate resilience.

The result, then, is a scenario made up of contrasting elements. In which, of course, there is no shortage of opportunities to develop suitable solutions to achieve a balance capable of reconciling population needs and environmental protection. This is suggested by a study published in Ecosystems and People that examined a phenomenon that has been little studied to date: brick mining in Antanarivo, Madagascar.

More bricks, less rice paddies

“Peri-urban areas are witnessing some of the most rapid transformations worldwide, marked by the conversion of agricultural land into urbanised zones,” the study explains. In Antananarivo, the scientists continue, this phenomenon has led to the conversion of rice paddies into areas where land extraction for brick production has taken center stage.

Areas dedicated to rice cultivation, in short, gradually turned into artificial swamps, then into raised gardens and finally into building areas.

In recent years, paddy fields have decreased by 58 percent, while brick production has increased by 68 percent. But what have been the consequences of this trend? “While prior research has investigated soil sealing and its impacts on Ecosystem Services (ES),” the academics explain, “the influence of soil extraction for building materials on other ES remains understudied.” Therefore, the research sought to explore this by thoroughly investigating the local context.

Landscape deteriorates while water availability improves

The investigation involved researchers from the universities of Antanarivo and Bern and the Swiss Federal Institute of Technology in Zurich. In total 263 interviews were conducted among farmers and brick producers in 9 local government units in 4 municipalities located southwest of the capital. The responses painted a rather varied picture in which negative aspects coexist with positive effects. The landscape, for example, seems to have deteriorated to the point that more than 6 out of 10 respondents perceive it to be worsening.

At the same time, however, two out of three people say they have experienced an improvement in terms of water availability for irrigation. This was due to the formation of new reservoirs as a result of soil extraction.

More difficult to assess, however, are the effects of mining on flood regulation: 35 percent of respondents noted positive effects. While 20 percent believed that excavation aggravated the risk of flooding.

New agricultural strategies

One of the most interesting aspects to emerge from the study is the impact of climate change on soil extraction. The presence of a longer dry season, respondents explained, has extended the time window for brick production but reduced the useful period for growing rice.

Farmers, in any case, have been able to adapt by resorting, for example, to direct seeding (as an alternative to transplanting the grain itself) and changing the agricultural calendar or the varieties grown.

Soil extraction, moreover, was accompanied by the spread of terracing and the use in agriculture of the peat soil that emerged through excavation. With these starting conditions, crops proved productive and resilient to flooding.

Soil extraction from problem to opportunity

The study, in short, showed how the implementation of sustainable agricultural practices has helped transform soil extraction from a problem into an opportunity for more balanced urbanization. “Our findings reveal that soil extraction can serve as an adaptation strategy to cope with challenges posed by climate change,” the scientists conclude.

Therefore, “policymakers should recognize the significance of brick-making for livelihood in times of crisis.” Finally, regulations “should prioritize sustainable soil extraction practices, protecting vulnerable lowlands from excessive flooding and targeting areas where soil extraction can bring benefits, such as improving access to more fertile soil layers for agriculture.”