23 May, 2024, Leioa. – A recent study analyses the resilience of forests after long-term mining activities and concludes that their ecological restoration requires more than 150 years. The research, led by BC3, also highlights the urgent need to consider more sophisticated metrics for assessing the health and resilience of ecosystems to human disturbance.

In a global effort to counter biodiversity loss and ecosystem degradation, ecological restoration strategies are gaining momentum around the world. However, restored ecosystems do not always achieve the biodiversity and functionality of undisturbed ones. One reason for this limited success may be the focus on short-term recovery of simple attributes, such as species richness, or isolated ecosystem functions. These simplified metrics may underestimate the real time that ecosystems need to recover. 

A new study published in the scientific journal Plant and Soil and led by Cambridge University researcher and BC3 Adjunct Researcher Asun Rodríguez Uña, closely examined the recovery of interactions between ectomycorrhizal fungi and beech trees in two open-cast iron mines in Artikutza, Navarra, in use since the 14th century and abandoned for more than 100 and 150 years, respectively. These fungi grow around the root tips of most trees in temperate and boreal forests, transferring essential nutrients to them in exchange for carbon. In this work they found that the species richness and diversity of these ectomycorrhizal fungi recovered to values comparable with the surrounding undisturbed forest, while the species composition remained different. Certain functional traits of these fungi (such as mycelial and sporocarp exploration types) also reached undisturbed values. Differences in soil pH and NH4+ affected the composition of ectomycorrhizal communities associated with beech, suggesting that mining caused a long-term impact on soil biogeochemistry, directly affecting beech-ectomycorrhizal fungal interactions.

“The recovery of these interactions is vital for the health and functioning of forest ecosystems. These findings challenge conventional conceptions about the long-term recovery of forests after human disturbance,” explains Asun Rodríguez Uña, lead author of the study.

The results also highlight that traditional metrics with low levels of ecological information, such as species richness and diversity, can significantly underestimate the true need for ecosystem recovery. After more than a century of mining abandonment, a remarkable recovery in species richness and diversity of beech-associated ectomycorrhizal fungi was observed. However, although these metrics reflected similar values to those of the surrounding unexploited forests, the species composition remained different in the former mines.

“Although ecosystems may appear to have recovered after several decades according to traditional metrics, full recovery may not have been achieved. It is essential to study more complex metrics, such as biotic interactions, over longer time scales in order to capture the full complexity of ecosystems and provide more accurate estimates of how long forests actually need to recover their resilience to cope with increasing changing conditions and extreme events resulting from global change,” emphasises Asun Rodríguez Uña, Adjunct Researcher at BC3.

Research such as this, which pioneers the study of ecosystem recovery at centennial time scales rather than over a few years, as is often the case, is particularly relevant and necessary today, given the increasingly ambitious global restoration initiatives. These strategies aspire to restore large tracts of forest across the planet in a matter of a few decades, when, in fact, this study emphasises the need to adapt these promising initiatives to the centennial time scales that forests actually require to recover their complexity and resilience to global change. Consequently, Rodríguez Uña further recommends caution in promoting restoration as a tool to reverse forest loss, to the detriment of protecting the conserved forests that still exist, especially primary forests, as they may be irreplaceable over time scales that go beyond several centuries. 

Paper details:

Title: Century-long recovery of mycorrhizal interactions in European beech forests after mining

Link: https://link.springer.com/article/10.1007/s11104-024-06665-z  

Doi: 10.1007/s11104-024-06665-z

Authors: Rodríguez-Uña, A., Salcedo, I., Rodríguez-Echeverría, S. et al.