Europe’s forests are losing orchids but gaining roses

A detailed study recently published in the journal New Phytologist reveals how understory species in Europe have changed in the last four decades. According to a team led by Josep Padullés, a CREAF researcher and temporary part-time lecturer at the Autonomous University of Barcelona, plant diversity in European forests has remained stable over the time in question. However, there have been more extinctions in particular groups, such as Ericaceae (heathers), Fabaceae (legumes) and Orchidaceae (orchids), while species from other families, such as Amaranthaceae (amaranths, spinach and similar), Cyperaceae (sedges) and Rosaceae (roses and similar), have made gains. An analysis of evolutionary lineages showed that the species in decline are closely related in the evolutionary tree, whereas those that have been newly acquired are more diverse in origin. The study also showed that human activities have played a major role in this slow, invisible change. 

Plants of high conservation concern, such as orchids, are in decline because of environmental changes caused by human activity.

“Plants of high conservation concern, such as orchids, are in decline because of environmental changes caused by human activity,” said Josep Padullés. “Those changes pose a threat to entire families of plants that have specific strategies for surviving and thriving in their environment,” he continued. “Our study has enabled us to see that relationship and obtain more valuable information than the study of individual species would have given us. Each family of species has its function in the ecosystem, so any alteration can have significant repercussions for the environment.” 

“Each family of species has its function in the ecosystem, so any alteration can have significant repercussions for the environment.”

JOSEP PADULLÉS, CREAF researcher, temporary part-time lecturer at the Autonomous University of Barcelona, and lead author of the study. 

Contrastingly, taller plants that require more nitrogen (e.g. some of the Rosaceae family and certain types of amaranths) have become more common in temperate forests. As such plants become more widespread, the study warns, they could change the way whole forests grow and function. 

For the study, the research team carried out high-precision analyses of 2672 different sites over approximately 40 years, closely observing variations in plant diversity. 

Human impact 

The study shows that human activities — from forest management and livestock grazing to the deliberate introduction of species — are a key factor in the change of Europe’s understory. People have altered ecosystems to the benefit of some species and the detriment of others. Although such alterations may seem modest, they have affected vegetation, speeding up extinctions or paving the way for new colonizations. “Forest management, for example, can change the extent of tree canopy cover, resulting in there being more or less shade, which, in turn, benefits different species,” explained Padullés. “Livestock farming has an impact on forests too, because animals have preferences for particular species and can compact the soil,” he added. Gramineae and Cyperaceae species have profited from forest management practices, for instance. 

Surprisingly, the study found that other climatic factors, such as warmer summers or excess nitrogen, were not the main drivers of the changes identified. Plant diversity actually increased at sites where winters became milder and annual precipitation rose, highlighting the complex interaction of different environmental factors. 

Scientific article

Padullés Cubino, J., Lenoir, J., Li. Avaluating plant lineage losses and gains in temperate forest understories: a phylogenetic perspective on climate change and nitrogen deposition. New Phytologist. DOI: https://doi.org/10.1111/nph.19477