Characterising roadside ecosystems using the SEEA Ecosystem Condition Typology: towards a core set of biophysical variables

Roadsides represent one of the most extensive anthropogenic networks globally, yet no integrative framework currently supports their systemic ecological characterisation and condition assessment. These areas can mitigate the environmental impacts of roads; yet this potential requires a clearer understanding of their functioning. While the System of Environmental-Economic Accounting – Ecosystem Accounting (SEEA-EA) framework and its Ecosystem Condition Typology (ECT) have been applied to coastal, forest and freshwater ecosystems, roadsides remain largely unaddressed within this framework, as they are primarily regarded as extensions of transport infrastructure rather than as distinct ecosystems. This study presents the first application of the SEEA-ECT to roadside ecosystems, combining a compartmental systems perspective with a systematic literature review for the 1950- 2024 period of 97 peer-reviewed studies. Thirty key biophysical variables are identified and organised across five compartments — air, soil, water, flora and fauna — and classified according to ECT physical, chemical, compositional, structural and functional state classes. Results reveal consistent anthropogenic pressure gradients extending from the road edge outwards, cross-compartment interactions driven by biogeochemical cycling, hydrological dynamics and microtopographic control and the central role of soil and flora as intermediary nodes linking pressures to ecosystem responses. Building on these findings, a preliminary core set of 10 biophysical variables is proposed, combining literature-based prioritisation with considerations of ecological relevance and complementarity across ECT classes. This set provides an initial basis for roadside ecosystem condition monitoring and requires further field validation. This framework offers a transferable and internationally standardised foundation for evidence-based roadside management, ecosystem condition accounting and sustainable infrastructure planning.