Health psychology and climate change: time to address humanity's most existential crisis.

Climate change is an ongoing and escalating health emergency. It threatens the health and wellbeing of billions of people, through extreme weather events, displacement, food insecurity, pathogenic diseases, societal destabilisation, and armed conflict. Climate change dwarfs all other challenges studied by health psychologists. The greenhouse gas emissions driving climate change disproportionately originate from the actions of wealthy populations in the Global North and are tied to excessive energy use and overconsumption driven by the pursuit of economic growth. Addressing this crisis requires significant societal transformations and individual behaviour change. Most of these changes will benefit not only the stability of the climate but will yield significant public health co-benefits. Because of their unique expertise and skills, health psychologists are urgently needed in crafting climate change mitigation responses. We propose specific ways in which health psychologists at all career stages can contribute, within the spheres of research, teaching, and policy making, and within organisations and as private citizens. As health psychologists, we cannot sit back and leave climate change to climate scientists. Climate change is a health emergency that results from human behaviour; hence it is in our power and responsibility to address it.

Biodiversity conservation as a promising frontier for behavioural science.

Human activities are degrading ecosystems worldwide, posing existential threats for biodiversity and humankind. Slowing and reversing this degradation will require profound and widespread changes to human behaviour. Behavioural scientists are therefore well placed to contribute intellectual leadership in this area. This Perspective aims to stimulate a marked increase in the amount and breadth of behavioural research addressing this challenge. First, we describe the importance of the biodiversity crisis for human and non-human prosperity and the central role of human behaviour in reversing this decline. Next, we discuss key gaps in our understanding of how to achieve behaviour change for biodiversity conservation and suggest how to identify key behaviour changes and actors capable of improving biodiversity outcomes. Finally, we outline the core components for building a robust evidence base and suggest priority research questions for behavioural scientists to explore in opening a new frontier of behavioural science for the benefit of nature and human wellbeing.