Offsetting policies have increased worldwide, utilizing a range of biodiversity metrics to compensate for development impacts. We conducted a global analysis of offset legislation by reviewing policies from 108 countries, which have voluntary offsets, or which require offsets by law. We sought to understand how well biodiversity metrics and offset currencies are documented in current policies. Where biodiversity metrics are documented we aimed to understand how metrics were scored, combined, and multiplied to create offset currencies. We found only 22 jurisdictions (from 14 countries) had guidelines documenting how biodiversity should be assessed during offsetting, representing a significant gap in the guidance available for offsets. Of the 22 guidelines, 14 (63%) documented use of aggregated currencies, eight (23%) did not aggregate biodiversity metrics into a single currency, and three (17%) did not specify either approach. Habitat type and condition, as well as area, were widely recommended across policies (>50%). Where species-level metrics were considered, guidelines generally focused on habitat distributions rather than abundance or population metrics. The lack of consistent and clear guidance about how biodiversity should be measured in offsets reduces our ability to determine the effectiveness of offsets in compensating for development impacts long term.
Artisanal and small-scale gold mining (ASGM), a wealth-generating industry in many regions, is nonetheless a global challenge for governance and a threat to biodiversity, public health, and ecosystem integrity. In 2019, the Peruvian government mobilized a targeted, large-scale armed intervention against illegal ASGM, which has caused deforestation and water resource degradation in this Tropical Biodiversity Hotspot. Before the intervention, the extent of waterbodies created by mining (mining ponds) was increasing by 33%–90%/year; after, they decreased by 4%–5%/year in targeted zones. Mining activity indicators showed 70%–90% abandonment. New mining activity accelerated in nearby areas outside the targeted area (pond area increases: 42%–83%; deforestation increases +3–5 km2/year). Far from intervention zones, mining remained stable during the study period. Our analysis demonstrates that targeted, large-scale government intervention can have positive effects on conservation by stopping illegal mining activity and shifting it to permitted areas, thereby setting the stage for governance. Continued conservation efforts must further address the impacts of informal mining while (1) limiting environmental degradation by legal mining; (2) remediating former mining areas to reduce erosion and enable reforestation or alternative uses of the landscape; and (3) sustaining such efforts, as some miners began to return to intervention areas when enforcement relaxed in 2022.