Published: February 2025

Sharing some knowledge and insights from recent research in the fascination fog oases forest of Chile

My initial encounter with the “arrayan” tree species Myrcianthes ferreyrae occurred during my final year at university. During a conference, a professor mentioned the existence of this endemic tree, emphasizing its restricted distribution to certain “fog oasis” of Arequipa, Peru. Intrigued by this information, and armed only with a printed photograph and a few coordinates, I embarked on a journey with two friends in 2011 to explore these fog oases in search of this remarkable species.

Fog oases, also known as coastal lomas, are isolated plant communities sustained by the deposition of advective fog, which occurs on steep coastal slopes below 1000 meters above sea level. These unique ecosystems are found at elevations ranging from 200 to 1200 meters and are distributed like islands within the hyperarid Peruvian-Chilean coastal desert, extending from 7° to 30°S in South America.

Each fog oasis is unique, varying in plant composition, size, topography, and proximity to the ocean. Plant endemism within these oases is notable, estimated at approximately 30% in Peru and 67% in Chile.

The vegetation of fog oases is dominated by a mixture of annual and perennial grasses, herbs, shrubs, and small populations of trees. Among these, the presence of tree species in fog oases stands out as particularly remarkable. Some tree species found in fog oases include Caesalpinia spinosa, Capparis prisca, Acacia macracantha, and Myrcianthes ferreyrae. Their branches often host an abundance of mosses and lichens, which provide a substrate for the growth of ferns, and epiphytes like Peperomia sp. and Tillandsia sp. Coastal fog is intercepted by the treetops and their associated epiphytes, where water droplets condense and travel down the tree trunks to the ground. This process significantly alters microclimatic conditions in this hyperarid desert, creating a more favorable environment for the establishment and growth of various plant species.

Myrcianthes ferreyrae, a perennial species of the Myrtaceae family, is found at elevations ranging from 100 to 1,000 meters above sea level in some localities of the Caravelí province in Arequipa, Peru. This species was described by McVaugh in 1958. In addition to being both endemic and rare, it is classified as Critically Endangered (CR), highlighting its critical conservation status. Historically the “arrayan” forest was continuous along the fog oases of Atiquipa and Taimara. The last decades several authors have reported a low population density for this species. The most recent inventory, conducted in 2012, of its population reported only 586 individuals, in addition to a considerable number of individuals cut down and dead standing. As good news, some of the trees recorded in the 2012 census are still standing in 2024. Although we have not conducted a new tree census, we hope to do so by applying for new funding.

Fog oases face significant threats from land use changes, including deforestation, overgrazing and urban expansion. These anthropogenic pressures are aggravated by climate changes, such as increasing temperatures and decreasing precipitation in coastal regions, which accelerate desertification processes. Consequently, these changes drive the loss of biodiversity, as well as ecosystem functions and services. In particular, overgrazing, a practice that has persisted since colonial times, continues to place considerable pressure on these fragile ecosystems, further exacerbating their vulnerability to environmental change. Myrcianthes ferreyrae encounters additional challenges due to its low natural regeneration capacity. This limitation is linked to its recalcitrant seeds and the effects of herbivory, which impede seedling establishment. In Atiquipa coastal lomas, some local residents have made efforts to propagate the species using seeds and traditional methods.

However, these practices are being lost. Another significant concern is the limited knowledge of the ecology and biology of M. ferreyrae, as well as its ecological role, which further complicates its conservation.

Last year, as part of my doctorate, I studied the climatic and biogeographical drivers that shapes the communities in fog oases. It was made possible thanks to my first encounter with fog oasis while studying the “arrayan”. Currently, I am evaluating whether positive interactions occurs in fog oases. To this end, we are working with plots, collecting soil samples, analyzing functional traits, and measuring changes in species richness within and outside potential facilitator species.

We aspire that our published work studying fog oasis, as well as our future findings, can contribute to the knowledge of species like the “arrayan”, which form part of these unique ecosystems that are so threatened by climate change and desertification. This brief note is an invitation for readers of this newsletter to take an interest in these incredible ecosystems and the species they host.

This work in coastal lomas was supported by the E032-117-2017 Doctorate Scholarship Grant from PROCIENCIA/CONCYTEC-PERU. Post written by Fiorella Gonzales Guillen (fiolitagonz@gmail.com).