Functional traits are commonly used to explain species distribution and ecosystem function. At the same time, humans are dramatically shaping the distribution and abundance of plants, and ecosystem function globally, through processes such as climate change, urbanization and agriculture. Yet people remain largely absent from existing trait frameworks. This limits the utility of trait-based models of ecosystem function and service supply, particularly the predictive models that are needed to respond to global environmental change. Calls have been made for new plant trait frameworks that incorporate humans to improve these models and predictions. Achieving this will benefit biodiversity and human wellbeing through better ecosystem management. Response traits, that explain how plants respond to environmental pressures, have been distinguished from effect traits, that explain effects on ecosystem functions and the supply of ecosystem services. Humans can be added to this response-effect trait framework, adding feedback loops linking perceived traits and services with management actions. Humans actively manipulate environments and plant traits to promote traits perceived to be desirable such as nativeness (or limit undesirable traits such as invasiveness) and aesthetic attributes, thus acting as filter on plant community assembly. Humans also manipulate traits and environments to deliver particular bundles of ecosystem services. Importantly, context has not been adequately addressed in existing studies and there are important ontological questions to address. Factors such as cultural background and socioeconomic status may mediate people-trait relationships; the trait 'reality' perceived by people varies across different knowledge systems - Indigenous Australians may perceive traits differently than ecologists or gardeners. People may perceive different service benefits in response to the same plant traits, and therefore may choose to manipulate plants or environments in different ways. Similarly, these perceptions and actions may vary with land-use/land-cover (e.g. conservation reserves vs agricultural areas vs gardens), and with climate (as trait responses vary with initial conditions). Most ecosystems in the world are now being managed by people for a range of objectives including conservation, food production and amenity. Incorporating humans into a coherent plant trait framework will improve functional understanding and management of diverse natural and human-dominated ecosystems across Australia and around the world, and improve predictions of how social-ecological systems will respond to global environmental change.
