Toxic pollution builds up in snake scales: what we learnt from black mambas – The Conversation

Report on Black Mambas as Bioindicators for Heavy Metal Pollution and Implications for Sustainable Development Goals

Introduction

Recent research conducted in the eThekwini Municipality, South Africa, has identified the black mamba (Dendroaspis polylepis) as a potent bioindicator for heavy metal pollution. As apex predators, these snakes play a crucial role in their ecosystems by controlling rodent populations, which indirectly supports SDG 2 (Zero Hunger) by protecting crops and SDG 3 (Good Health and Well-being) by limiting disease spread. This study demonstrates their new potential as a non-invasive tool for monitoring environmental health, directly contributing to the achievement of SDG 11 (Sustainable Cities and Communities) and SDG 15 (Life on Land).

Methodology of the Study

Bioaccumulation and Bioindicators

The study is based on the principle of bioaccumulation, where toxins concentrate in organisms over time. As predators high on the food chain, black mambas accumulate heavy metals present in their prey, making them an effective bioindicator species for assessing ecosystem health. This monitoring capability is vital for achieving sustainable environmental management as outlined in several SDGs.

Study Area and Sample Collection

The research was focused on the greater Durban area, a region characterized by a mix of heavy industry and protected green spaces known as the Durban Metropolitan Open Space System. This setting provides a clear contrast for evaluating pollution levels, aligning with the goals of SDG 11 (Sustainable Cities and Communities) to manage urban environmental impact.

• Samples were collected from 31 deceased mambas (muscle and liver tissue).
• Non-invasive scale clippings were taken from 61 live snakes.

Targeted Pollutants

Four specific heavy metals were tested due to their prevalence in industrial processes and severe health impacts, a direct concern for SDG 3 (Good Health and Well-being) and SDG 12 (Responsible Consumption and Production).

1. Arsenic: Can cause cancer and skin lesions.
2. Cadmium: Harms kidneys and bones.
3. Lead: Affects brain development and blood functions.
4. Mercury: Primarily damages the nervous system.

Key Findings and Analysis

Validation of Non-Invasive Methods

A primary finding was the strong correlation between heavy metal concentrations in harmlessly collected scale clippings and those in internal tissues (liver and muscle). This validates the use of scale clippings as a reliable, non-invasive method for monitoring pollution, which is critical for ethical wildlife research and the conservation objectives of SDG 15 (Life on Land).

Pollution Levels and Geographic Variation

The results demonstrated a clear link between land use and pollution levels, reinforcing the objectives of SDG 11 (Sustainable Cities and Communities).

• Snakes from industrial and commercial areas showed significantly higher concentrations of arsenic, cadmium, and lead.
• Snakes from natural sites within the Durban Metropolitan Open Space System had significantly lower concentrations of these toxins.
• Mercury levels showed less variation, likely due to its ability to travel more widely through the environment.

Implications for Sustainable Development Goals

SDG 3: Good Health and Well-being & SDG 6: Clean Water and Sanitation

The black mambas act as sentinels, providing an early warning system for pollution that threatens both environmental and human health. The presence of these heavy metals in wildlife indicates contamination of soil and water sources, posing a direct risk to human populations and undermining efforts to ensure clean water and public health.

SDG 11: Sustainable Cities and Communities

This research provides city managers and urban planners with a cost-effective tool to monitor the environmental impact of industrial activity. The findings underscore the critical importance of maintaining and expanding urban green spaces, which act as buffers against pollution and contribute to healthier, more sustainable cities.

SDG 15: Life on Land

By establishing a snake species as a bioindicator, this study offers a new methodology for monitoring the health of terrestrial ecosystems. This approach helps in tracking the impact of pollution on biodiversity and supports the development of strategies to halt ecosystem degradation, a core target of SDG 15.

Conclusion

The study successfully establishes the black mamba as a viable and effective bioindicator for heavy metal pollution in Africa. The use of non-invasive scale clippings presents an ethical and practical method for environmental monitoring. The findings serve as a clear warning about the dangers of industrial pollution and provide a scientific basis for municipal authorities to implement policies that protect both environmental and human health, thereby advancing multiple Sustainable Development Goals.

Analysis of the Article in Relation to Sustainable Development Goals

1. Which SDGs are addressed or connected to the issues highlighted in the article?

• SDG 3: Good Health and Well-being

  The article directly connects heavy metal pollution to human health risks. It states that the pollutants pose a danger to “ultimately human health” and details the specific negative effects of the tested metals: “Mercury primarily damages the nervous system, arsenic can cause cancer and skin lesions, cadmium harms kidneys and bones and lead mainly affects brain development and blood functions.”

• SDG 6: Clean Water and Sanitation

  The research addresses water and soil pollution. The article explains that toxins from human activities “pollute water or soil and gradually accumulate in plants and animals.” This highlights the contamination of water resources, which is a core concern of SDG 6.

• SDG 11: Sustainable Cities and Communities

  The study is set within the eThekwini Municipality (Durban), a major city with a “large industrial sector.” The research contrasts pollution levels between industrial areas and the city’s green spaces (“Durban Metropolitan Open Space System”), directly addressing the environmental impact of urban and industrial activities. The article concludes by noting that the responsibility to act on these findings lies with “the municipality and city managers.”

• SDG 12: Responsible Consumption and Production

  The source of the pollution is identified as “waste products of human activities like manufacturing,” including “chemicals, petrochemicals and automotive manufacturing.” This points to unsustainable production patterns that release hazardous chemicals into the environment, a key issue addressed by SDG 12.

• SDG 15: Life on Land

  The article’s central theme is the impact of pollution on a terrestrial species, the black mamba, and its ecosystem. It discusses how toxins bioaccumulate in the food chain, affecting wildlife. The research also highlights the importance of snakes as “vital players in their ecosystems” and the value of green spaces for maintaining environmental health, which are central to protecting biodiversity and terrestrial ecosystems.

2. What specific targets under those SDGs can be identified based on the article’s content?

1. Target 3.9: Substantially reduce deaths and illnesses from hazardous chemicals and pollution

   The article focuses on identifying and measuring hazardous chemicals (arsenic, cadmium, lead, mercury) known to cause severe illnesses. The research provides a method to monitor this pollution, which is the first step toward reducing its impact on human health.

2. Target 6.3: Improve water quality by reducing pollution

   The study implicitly addresses this target by investigating pollutants that contaminate water and soil. By using snakes as bioindicators, the research offers a tool to monitor the extent of chemical pollution in local environments, which is essential for efforts to improve water quality.

3. Target 11.6: Reduce the adverse per capita environmental impact of cities

   The research conducted in Durban directly measures the environmental impact of urban industrial activity. The findings, which show higher toxin levels in industrial areas compared to green spaces, provide city managers with data to address and reduce urban pollution.

4. Target 12.4: Achieve the environmentally sound management of chemicals and all wastes

   The article is centered on the consequences of the release of heavy metals from industrial waste. The study’s method of using bioindicators serves as a monitoring system for the release of these chemicals into the “air, water and soil,” directly supporting the goal of managing chemical waste to minimize its impact on health and the environment.

5. Target 15.5: Take urgent action to reduce the degradation of natural habitats and halt biodiversity loss

   Pollution is a primary driver of habitat degradation. The article shows how heavy metals contaminate ecosystems, affecting wildlife like the black mamba. By providing a way to detect and measure this degradation, the research supports actions to protect natural habitats and the biodiversity within them.

3. Are there any indicators mentioned or implied in the article that can be used to measure progress towards the identified targets?

• Concentration of heavy metals in bioindicator species

  The primary indicator presented in the article is the concentration of specific heavy metals—arsenic, cadmium, lead, and mercury—in the tissues of black mambas. The research validates the use of non-invasive scale clippings as a reliable method for this measurement. The article states, “We found that the heavy metal concentrations in scales correlated with those found in the muscle and liver samples.” This quantifiable data can be used to:

  • Measure the level of environmental contamination in specific locations, as shown by the comparison between industrial areas and natural sites.
  • Track changes in pollution levels over time to assess the effectiveness of pollution control measures.
  • Monitor the health of ecosystems and the impact of pollution on wildlife, directly measuring progress towards reducing environmental degradation.

4. Summary Table of SDGs, Targets, and Indicators

Source: theconversation.com