Biodiversity is defined by the Convention on Biological Diversity (CBD) as “the variability among living organisms from all sources including, inter alia, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part; this includes diversity within species, between species and of ecosystems” [22]. Here, we use biodiversity in a broad sense to include the composition, configuration and diversity of specific species or habitats; the abundance and biomass of species; the functional traits of species (e.g. nutrient content, medicinal properties, colours, sounds, contagious properties); and the genetic composition (e.g. SARS-CoV-2) and identity of particular species (e.g. lion, robin, ticks, oak). In this article, the term ‘biodiversity’ will frequently be used in the text as shorthand for these elements of biodiversity. Importantly, biodiversity is more than just the amount of nature or greenspace. Nature as defined by Hartig et al. [11] refers to “physical features and processes of nonhuman origin that people ordinarily can perceive, including the “living nature” of flora and fauna, together with still and running water, qualities of air and weather, and the landscapes that comprise these and show the influence of geological processes”. The term greenspace is defined as outdoor areas dominated by vegetation (e.g. parks) or isolated green elements (e.g. street trees) [23]. These broad terms, which are often used in studies investigating the health benefits of natural environments, can limit the understanding of how variation in the ecological characteristics of the natural environment relates to health.