After the gold rush: Biodiversity communities in abandoned gold mines and implications for restoration

Artisanal small-scale gold mining (ASGM) is responsible for 90% of the forest loss within the Guiana Shield, making it a significant environmental concern for Guyana's ecosystems. Despite its environmental impact, ASGM remains a key contributor to the country's economy. However, the consequences of this activity on biodiversity, particularly in terms of recovery, are still poorly understood. There is also a notable lack of evidence-based research on the conservation value of abandoned gold mines and their role in the recovery of surrounding ecosystems. This thesis addresses these gaps by investigating the impacts of ASGM on biodiversity communities in Guyana's forests, with a particular focus on the natural recovery of ecosystem services and species following mining cessation. I conducted fieldwork across 16 abandoned gold mines in the northwest of Guyana, which vary in terms of years since abandonment and mine areal size. The research examines the effects of mining on localised microclimates and on two taxa, understory birds and dung beetles, both of which serve as excellent bioindicators of disturbance and recovery. Using a combination of field-based ecological surveys and remote sensing techniques, I assess microclimatic changes, species responses, and the potential signs of recovery in abandoned mined landscapes.

Firstly, I investigated the microclimatic changes associated with ASGM, using satellite imagery and ground-based measurements of temperature and vapour pressure deficit (VPD) alongside vegetation data. I reveal how gold mining creates distinct microclimatic conditions at the centre of the mine, the edge of the mine and 100 m from the edge of the mine. Temperature increased with reduced canopy cover meaning that the centre of the mine exhibited very high temperatures of up to 50.5°C. Over time, mine centres became significantly drier, as shown by a strong positive relationship between VPD and years since abandonment. I also show slow recovery of vegetation with some recovery at the edges of mines but no significant tree growth within the centre of the mines.

Secondly in Chapter 3 I examine the recovery of understory bird communities post-mining, assessing how community composition and habitat use are influenced by ASGM. I highlight the slow recovery of bird populations and reveal how forest-dependent species are replaced by generalist in mined areas. I also reveal that canopy cover loss is the most important factor for maintaining forest-dependent bird communities and plays a role in their recovery within mined landscapes. I also reveal that after 100 m from the edge of mines that bird communities are not impacted by mining-induced edge effects.

In Chapter 4 I focus on dung beetles, a key bioindicator of ecosystem health and disturbance. By applying the same methodology developed in Chapter 3, I investigate how dung beetle communities respond to ASGM and explore the effects of microclimatic changes on their distribution and diversity. The study confirms dung beetles as effective indicators of disturbance, with strong negative responses to mining. I reveal that both canopy cover loss and increased temperatures reduce both the abundance and species richness of dung beetles, as well as the amount of mining within a 500 m buffer. I also did not find any signs of recovery in dung beetle communities following the cessation of mining.

Building on these findings, Chapter 5 compares the impacts of ASGM to other land-use activities in Guyana, including urbanisation and Reduced Impact Logging (RIL), by analysing species richness and beta diversity across the different land-use types. The comparative analysis offers insights into the relative severity of gold mining on bird diversity compared to other human-induced land-use changes. My findings reveal that ASGM sits in between RIL and urbanisation for the number of species lost by habitat modification, with high levels of turnover indicating species replacement by generalists. I reveal that ASGM reduces forest-dependent species by 50% which was 10 times higher than the losses found within RIL sites.

The findings of this thesis is one of the first to assess the impacts of ASGM on the surrounding biodiversity communities. It underscores the importance of understanding the long-term impacts of ASGM on biodiversity, particularly in terms of slow recovery and disrupted ecosystem functions. My research highlights the need for active restoration strategies, especially to restore canopy cover, and sustainable land management practices to mitigate the ecological consequences of mining. The thesis contributes to the growing body of knowledge on post-mining recovery in tropical ecosystems and provides evidence-based recommendations for policymakers to support biodiversity conservation and restoration efforts in Guyana and the wider Amazon region.