Richard Stafford

Carbon offsetting is currently a major tool in managing carbon emissions and informing sustainability plans of organisations in the drive to net-zero. This study aims to identify the offsetting potential of existing conservation schemes, and whether carbon offsetting credits could provide finance these conservation activities. The results from Dorset, in the UK, indicate that many existing conservation schemes in woodlands, heathlands, and grasslands cannot only enhance biodiversity but also capture significant amounts of carbon, and while habitats differ by region and country, the general results should be applicable elsewhere. We show that the cost per additional tonne of carbon sequestered as a result of conservation activities varies considerably between different conservation projects. On average, across the conservation projects we studied, the cost of this offsetting is GBP 80 per tonne CO2e sequestered and ranging between GBP 120 and GBP 0, depending on the project and whether existing biodiversity grants would be available. However, this figure was based on adapting and refining the existing conservation projects and did not involve expensive factors, such as purchase of land, which make the prices potentially unrealistic, especially in a Global North context. While the costs identified are higher than many offsetting schemes at present, it could present a useful option for those wishing to localise their offsetting. The concept is highly scalable and could remove significant amounts of carbon dioxide. Combining the approach with biodiversity credits or other credit schemes could make the higher costs more attractive to potential buyers.

Historical data on co‐occurring taxa are extremely rare. As such, the extent to which distinct co‐occurring taxa experience similar long‐term patterns in species richness and compositional change (e.g., when exposed to a changing environment) is not clear. Using data from a diverse ecological community surveyed in the 1930s and resurveyed in the 2010s, we investigated whether local plant and insect assemblages displayed cross‐taxon congruence—that is, spatiotemporal correlation in species richness and compositional change—across six co‐occurring taxa: vascular plants, non‐vascular plants, grasshoppers and crickets (Orthoptera), ants (Hymenoptera: Formicinae), hoverflies (Diptera: Syrphidae), and dragonflies and damselflies (Odonata). All taxa exhibited high levels of turnover across the ca. 80‐year time period. Despite minimal observed changes at the level of the whole study system, species richness displayed widespread cross‐taxon congruence (i.e., correlated temporal change) across local assemblages within the study system. Hierarchical logistic regression models suggest a role for shared responses to environmental change underlying cross‐taxon correlations and highlight stronger correlations between vascular plants and their direct consumers, suggesting a possible role for biotic interactions between these groups. These results provide an illustration of cross‐taxon congruence in biodiversity change using data unique in its combination of temporal and taxonomic scope, and highlight the potential for cascading and comparable effects of environmental change (abiotic and biotic) on co‐occurring plant and insect communities. However, analyses of historical resurveys based on currently available data come with inherent uncertainties. As such, this study highlights a need for well‐designed experiments, and monitoring programs incorporating co‐occurring taxa, to determine the underlying mechanisms and prevalence of congruent biodiversity change as anthropogenic environmental change accelerates apace.