In 2020, the COVID-19 pandemic upended international trade. Countries shut their borders, breaking the webs of supply chains that crisscross the globe. These systems of people, organisations and companies work to supply consumers with products, such as mobile phones, or services, like transportation. While some supply chains have since returned to a semblance of normality, understanding their extent—and how they interact—may be vital if humanity wants to confront its other great challenge: climate change.