Summary:

- The article discusses the unexpected decline of nitrogen-fixing plants in European and American forests, which is a concerning trend for forest ecosystems.
- Nitrogen-fixing plants play a crucial role in maintaining soil fertility and supporting the growth of other plant species, but their populations have been declining in recent decades.
- The reasons for this decline are not fully understood, but the article suggests that factors such as climate change, land-use changes, and the spread of invasive species may be contributing to the problem.