The Silent Feast: How a Beloved Caterpillar Reflects Mining's Environmental Toll

The Caterpillar on Our Plate

Imagine a food that connects you to ancestral traditions, a culinary delight passed down through generations. In Botswana, the phane caterpillar (Imbrasia belina) represents exactly that—a seasonal treat harvested from the wild, rich in protein and cultural significance. But in the shadow of the Selebi Phikwe nickel-copper mine, this traditional food source tells a more complex story, one that reflects the environmental challenges of mining landscapes.

For decades, scientists have known that mining operations can release heavy metals into the environment. These elements don't simply disappear; they travel through soil, water, and air, eventually finding their way into plants and animals. What happens when these toxic substances enter traditional food sources? A groundbreaking study conducted around Selebi Phikwe sought to answer this question by investigating heavy metal concentrations in the beloved phane caterpillar, revealing concerning findings about environmental contamination and food safety ¹ .

Mining operations can release heavy metals into the environment, affecting surrounding ecosystems.

The Mining Landscape of Selebi Phikwe

Southern Africa holds substantial mineral wealth, accounting for nearly 30% of the world's discovered mineral reserves ¹ . Botswana's economy has benefited significantly from this resource abundance, with the Selebi Phikwe nickel-copper (Ni-Cu) mine standing as one of the country's earliest and most important mining operations ³ . For over 25 years, the mine and its smelter/concentrator plant processed valuable metals from ore bodies containing chalcopyrite (CuFeS₂), pentlandite ((Fe,Ni)₉S₈), and other sulphide minerals ³ .

While mining brings economic benefits, it also generates environmental challenges. The processes of extraction, smelting, and concentrating metals can release dust particles rich in heavy metals into the surrounding atmosphere ³ . These particles, known as Particulate Air Matter (PAM), settle on soils and vegetation, while mine drainage water can transport metallic ions into water systems ³ . Previous studies around Selebi Phikwe had already confirmed that mining activities affected the atmosphere, soils, and vegetation ^{3 6} , setting the stage for investigating how these contaminants might move through the food chain to reach the phane caterpillar—and potentially the people who consume them.

Tracking Metals Through the Food Chain: The Phane Study

To understand whether heavy metals from mining operations were accumulating in traditional food sources, researchers designed a comprehensive study examining multiple components of the local environment. The investigation focused on the area surrounding the Ni-Cu mine and smelter/concentrator plant in Selebi Phikwe, collecting samples at varying distances from the mining operations ⁶ .

A key aspect of the study design involved comparing samples collected closer to the mining and smelting operations with those obtained from further away. This distance-based approach helped researchers distinguish between background levels of heavy metals and those directly linked to mining activities.

Laboratory analysis allowed researchers to measure heavy metal concentrations at trace levels.

Revealing Results: Metals Where They Shouldn't Be

The findings from the study painted a concerning picture of environmental contamination. Analysis consistently showed higher concentration levels of heavy metals in samples obtained closer to the mine and smelter plant compared to those collected further away ⁶ . This pattern held true across different sample types—from soil and air to vegetation and caterpillars.

The presence of these metals in phane caterpillars represented a potential direct exposure pathway to humans, raising important questions about food safety and traditional harvesting practices in mining-affected regions.

From Soil to Caterpillar: The Contamination Pathway

How do heavy metals from deep underground end up in a caterpillar harvested from trees? The journey involves several steps, each representing a potential point where contaminants enter ecological systems.

The situation at Selebi Phikwe exemplifies a broader pattern seen in mining landscapes across Southern Africa. As noted in a review of aquatic ecological risks from degraded mining landscapes, "mining waste generated from industrial and artisanal mining has significantly affected the ecological integrity of SA aquatic ecosystems due to the accelerated introduction and deposition of heavy metals" ¹ . What makes the phane case particularly noteworthy is how this contamination has entered a traditional food resource with significant cultural importance.

The Scientist's Toolkit: How Researchers Measure Metal Contamination

Understanding heavy metal contamination requires sophisticated analytical techniques and careful methodology. The researchers investigating phane caterpillars around Selebi Phikwe employed a comprehensive approach to ensure accurate and meaningful results. Their "toolkit" included both field collection methods and laboratory analysis techniques.

The choice of analytical techniques is crucial in contamination studies. Methods like ICP-OES can detect metals at very low concentrations—sometimes as low as 1.00 × 10⁻⁴ mg/kg, as noted in a similar study on herbal concoctions in Botswana ⁴ . This sensitivity allows researchers to identify even trace amounts of heavy metals that might still pose health risks with long-term exposure.

The research approach also highlighted the importance of studying multiple environmental compartments simultaneously. By examining tailings, soils, air particulates, host plants, and the caterpillars themselves, scientists could trace the complete pathway of heavy metals from their source through the food chain, providing a comprehensive picture of the environmental impact.

Implications and Reflections: Beyond the Laboratory

The findings from the phane caterpillar study extend far beyond academic interest, touching on issues of public health, cultural preservation, and environmental management. The detection of heavy metals in a traditional food source raises important questions about safety and sustainability in mining-affected regions.

While the situation appears concerning, understanding these contamination pathways also opens opportunities for mitigation. Potential approaches might include identifying harvesting restrictions in heavily contaminated zones, developing remediation strategies for affected areas, and implementing more stringent emissions controls at mining operations. What remains clear is that the story of the phane caterpillar and the Selebi Phikwe mine serves as a powerful reminder of the interconnectedness of industrial activity, environmental health, and human traditions—a reminder that what we put into our environment eventually makes its way onto our plates.