Tag: climate mitigation

by Lorenzo Orzan

Across Europe, something quiet but powerful is happening. As people leave rural areas, forests are coming back, slowly reclaiming former meadows and pastures. At first glance, this seems like good news. More forests mean more carbon stored and, potentially, more biodiversity. But is it really that simple?

In our recent study across Italy, we followed this process from North to South, tracking how ecosystems change over time as forests naturally regenerate. By comparing sites at different stages, from open grasslands to forests up to 75 years old, we were able to reconstruct what happens when trees return.

The first answer is clear: carbon storage increases steadily. As forests grow, trees accumulate large amounts of carbon, becoming the main storage pool. In the oldest stands, carbon stocks can reach very high levels, highlighting the strong potential of natural reforestation for climate mitigation. But there is another side to the story: As forests close, light becomes scarce. Many herbaceous species that thrive in open habitats start to disappear. Across most of our study sites, plant diversity peaked in meadows and early stages and then declined as forests matured. In other words, gaining carbon often meant losing plant diversity. Yet, the picture is not entirely uniform. In the southernmost site, under Mediterranean conditions, plant diversity initially declined as forests became denser, but partially recovered again in the oldest stands, suggesting that mature forests can recreate suitable conditions for a richer understory vegetation. This suggests that, in some contexts, forests may eventually host both high carbon stocks and a richer understory. These findings highlight an important message for rewilding and land management: natural forest expansion is not automatically a win-win solution. It can involve trade-offs between climate mitigation and biodiversity conservation.

The challenge, moving forward, is to understand where and when these trade-offs can be reduced. Under the right conditions and given enough time, forests may offer opportunities to balance both goals. Until then, letting forests return remains a powerful tool, although it needs to be used with awareness of what we gain, and what we might lose along the way.

References: Orzan, L., Tomao, A., Antoniella, G., Bonari, G., Casolo, V., Chiti, T., Cingano, P., Foscari, A., Incerti, G., Panico, S. C., Piazza, N., Trotta, G., & Alberti, G. (Year). As forests reclaim the land: Latitudinal variations in carbon-biodiversity trade-offs under natural forest expansion in Italy. Forest Ecology and Management, Volume 605, https://doi.org/10.1016/j.foreco.2026.123527