Estimating the carbon footprint of citizen science biodiversity monitoring.
Across society there is pressure to assess and reduce carbon emissions to meet the obligations of the Paris Agreement and the Glasgow Climate Pact. Within the science community, there is increasing awareness of the carbon footprint of research activities, but to date there is no consideration of emissions associated with biodiversity monitoring. Biodiversity monitoring, often delivered through citizen science schemes, is key to assessing environmental change impacts and mitigation. However, attributes of rigorously designed schemes such as randomisation and high recording effort can require volunteers to undertake regular travel, raising two important questions: (a) is biodiversity monitoring reliant on volunteers with private vehicles?; and (b) what is the carbon footprint of a typical monitoring scheme? This study focussed on travel associated with participation in the UK Breeding Bird Survey. The BBS involves twice-annual surveys of a stratified random sample of 1-km squares across the United Kingdom, providing population trends for c. 120 terrestrial bird species with data used widely in policy and research. Using coverage information from 2019, we calculated road distances from volunteers' home addresses to their squares and sought information on travel methods using an online questionnaire (54% response rate). In 2019, 2765 volunteers made 7520 visits to 3914 1-km squares, travelling over 286,000 km in the process. Travel required to visit individual squares was highly skewed and differed geographically and according to mode of travel. Eighty-eight per cent of squares were accessed by private car, with conventionally fuelled vehicles accounting for 95% of these. Active travel accounted for 10% of visits and public transport only 1.4%. We estimate the total emissions produced to achieve BBS coverage in 2019 to be at least 46.8 tonnes CO2e. These results indicate a heavy reliance on access to private vehicles, creating a barrier to future participation, especially if pathways to decarbonisation involve reduced car ownership. Furthermore, they indicate the scale of carbon emissions likely to be produced by the monitoring sector. We discuss possible pathways to decarbonise monitoring schemes but stress that we do not wish to criticise the travel decisions of individual volunteers: the onus on decarbonisation lies firmly with the organisers of monitoring schemes.