Mapping the expansion of galamsey gold mines in the cocoa growing area of Ghana using optical remote sensing

Abstract

Artisanal gold mining (galamsey) and cocoa farming are essential sources of income for local populations in Ghana. Unfortunately the former poses serious threats to the environment and human health, and conflicts with cocoa farming and other livelihoods. Timely and spatially referenced information on the extent of galamsey is needed to understand and limit the negative impacts of mining. To address this, we use multi-date UK-DMC2 satellite images to map the extent and expansion of galamsey from 2011 to 2015. We map the total area of galamsey in 2013 over the cocoa growing area, using k-means clustering on a cloud-free 2013 image with strong spectral contrast between galamsey and the surrounding vegetation. We also process a pair of hazy images from 2011 and 2015 with Multivariate Alteration Detection to map the 2011-2015 galamsey expansion in a subset, labelled the change area. We use a set of visually interpreted random sample points to compute bias-corrected area estimates. We also delineate an indicative impact zone of pollution proportional to the density of galamsey, assuming a maximum radius of 10 km. In the cocoa growing area of Ghana, the estimated total area of galamsey in 2013 is 27,839 ha with an impact zone of 551,496 ha. In the change area, galamsey has more than tripled between 2011 and 2015, resulting in 603 ha of direct encroachment into protected forest reserves. Assuming the same growth rate for the rest of the cocoa growing area, the total area of galamsey in 2015 is estimated at 43,879 ha. Galamsey is developing along most of the river network (Offin, Ankobra, Birim, Anum, Tano), with downstream pollution affecting both land and water.

Criminalization of “galamsey” and livelihoods in Ghana: Limits and consequences

“…For example, Kervankiran, Dziwornu, and Temurçin (2016) study showed that galamsey activities contribute to the loss of agricultural lands, biodiversity loss, and reduction in rainfall patterns. Similarly, using remote sensing technology, Snapir, Simms, and Waine () estimated that galamsey activities in cocoa‐growing areas in Ghana more than tripled between 2011 and 2015, resulting in the encroachment of about 603 protected forest reserves. These expansions of galamsey activities are also known to pose threats to health due to poor safety procedures (Amankwah & Anim‐Sackey, ; Masterwille, ).…”

“…The idea of formalizing ASM is often a subject of intense debate because formalization varies across countries and contexts and has no clear-cut definition (Singo & Seguin, 2018). However, for this study, formalization means "to speak of individual and group rights: the right to mine, the right to land title, and the right to minerals" (Siegel & Veiga, 2009, p. 52).…”

“…there is now an emerging consensus that the formalization of the sector would not only allow for these associated problems to be addressed but also ensures that the sector contributes America (Hilson, 2017). It is estimated that about 30 million people in more than 70 countries around the world are directly engaged in ASM (Singo & Seguin, 2018;Owusu, Bansah, & Mensah, 2019). ASM is usually thought of as an informal poverty driven activity that involves rudimentary techniques of mineral extraction, hazardous working conditions, low capital investment and extensive manual labor (Hilson, 2002;Teschner, 2012).…”

Biomonitoring of Mercury in Hair among a Group of Eritreans (Africa)

“…In this way, Díez et al, [15] found that mean Hg levels were greater in people living close to industrial mining activity sites compared with a site placed hundreds of kilometers away. To our knowledge, in Africa, the impact of Hg contamination has not been thoroughly studied and the human exposure assessment has been very limited, despite the fact that artisanal and small-scale gold mining continues to expand and to increase in some hotspots in African countries, in response to the global demand for gold [12,[16][17][18].…”

Estimating the “Forgone” ESVs for Small-Scale Gold Mining Using Historical Image Data

“…Again, Snapir et al extensively mapped and discussed the spatial-temporal dynamics of "galamsey" activities. Their work revealed that the activity has tripled within four (4) years, from 2011 to 2015 and have directly encroached major forest reserves [17]. However, to be informed about the size and extent of degradation is inadequate when it comes to representing these degradation situation for policy implication purposes, yet, little has been ushered into quantifying the ecosystem services such as the food production, air purification, carbon storage, etc., that are lost due to these technological loads.…”