In nature, organisms of different species interact to form communities that control the functioning of ecosystems (nutrient cycling, fluxes of matter and energy, etc.). The functioning of ecosystems is central to humans as it underpins the production of food and support physical and mental wellbeing. But in the context of global change dynamics, the functioning of ecosystems is at increasing risk. To understand the resistance and resilience of ecosystems to global environmental threats, biologists are trying to link changes in the structure of natural communities to changes in the functions performed by these communities. In this seminar, I propose that the physics of networks is central to this endeavour. Biologists are asking questions such as: are there early signals of systemic crises? Is the system at a tipping point and possibly about to fall into alternative, degraded states? Are ecological networks rewiring in response to climate change, and what are the implications of their structural changes for ecosystem functioning? In this seminar, I will show examples of studies investigating natural networks such as food webs, and illustrate the current understanding of the stability properties of these networks. I will show the type of data we usually collect and try to boost a discussion around how the study of ecological networks could greatly benefit from network science.