What evidence exists on how biodiversity is affected by the adoption of carbon footprint-reducing agricultural practices? A systematic map.

Abstract

Background: The global agriculture sector is expected to contribute towards carbon net zero by adopting interventions to reduce/offset greenhouse gas emissions and increase carbon sequestration/removal. Many of these interventions require change to land management and agriculturally associated habitats, subsequently impacting biodiversity. This relationship is important as the Convention on Biological Diversity has also pledged to reverse nature decline. To understand this relationship, a systematic map was developed to collate evidence relating to the impacts of carbon footprint reducing interventions on agriculturally associated biodiversity. This systematic map collated studies from temperate farming systems including northern Europe, North America and New Zealand.

Methods: A protocol was published to define the methodology. Potentially relevant articles were identified by searching three academic databases using a predefined search string. Also, nine organisational websites were searched using key words. All potentially relevant articles were exported into EPPI-Reviewer-Web. Following deduplication, the remaining articles were screened at title and abstract level, partially with the aide of machine learning, before full text screening and extraction of metadata.

Review findings: Screening began with 67,617 articles that ended with an evidence base of 820 primary research studies and 82 reviews. The evidence base includes studies from 1978 to April 2024, of which 81% were studies that lasted less than 5 years. Whilst microorganisms (n = 328), arthropods (n = 190), worms (n = 121) and plants (n = 118) were well represented in the evidence base, other groups such as birds (n = 32), gastropods (n = 16), mammals (n = 13), amphibians (n = 1) and reptiles (n = 1) were represented less well. The most studied interventions were to increase soil organic carbon through reduced tillage (n = 227) and cover cropping (n = 136). However, there were less than five studies in total for the following land management objectives: avoiding soil compaction (n = 2), precision farming (n = 2) and renewable energy production. Study authors reported carbon footprint-reducing practices to positively impact biodiversity in 65% of studies, to have mixed effects in 11%, negative in 8% and no effect in 16% of studies. As no critical appraisal was carried out on the included studies, we recommend further study validation and synthesis in order to support these findings.

Conclusions: The evidence base has highlighted evidence clusters and gaps on how farming practices that can reduce the carbon footprint of a farm impacts agriculturally associated biodiversity. There are many areas for further research including studies investigating the long-term relationship of interventions that alter habitats over a long period such as rewetting peat soils and increasing tree cover. Future research should observe abundance and diversity of multiple species to generate a better understanding of an intervention's impact. The review evidence base largely matched the primary evidence base, however none were conducted with systematic methodologies. This systematic map is intended to direct further primary and secondary research to improve the understanding of how carbon footprint reducing practices impact biodiversity, thus contributing towards meeting the legally binding global environmental targets in concert.