Epiphytes are increasingly threatened by forest disturbances

Epiphytes are plants that can be found in tree canopies like mosses, orchids, and bromeliads. A recent study highlights the profound importance of epiphytes to global biodiversity, as well as the growing threats they face due to human and natural disturbances.

Known as nonparasitic plants that thrive on other plants, epiphytes serve vital functions in forests. They provide habitats in trees for a variety of life, ranging from microorganisms like bacteria to reptiles and birds.

Inherent characteristics 

Epiphytes showcase a remarkable diversity, with over 28,000 identified species. Mosses stand out as the most common type.

The inherent characteristics of epiphytes, which once facilitated their survival in forest canopies, now leave them increasingly susceptible to disturbances.

Rapid environmental changes are placing heightened pressure on these unique plants, noted Nalini Nadkarni, a biologist at the University of Utah who is known for her work on treetop ecosystems.

Vulnerability of epiphytes

In her latest study, Nadkarni emphasizes the heightened vulnerability of epiphytes to disturbances like climate change and deforestation. 

Alarmingly, she reveals that while many of these disturbances are labeled “natural,” human activities are intensifying their frequency and severity worldwide.

“This synthesis revealed the exceptional vulnerability to the increasing levels of disturbances – such as climate change and deforestation – on the abundance, diversity and connectivity of canopy-dwelling plants around the globe,” said Nadkarni. 

“Although we categorize the disturbances with greatest negative effects on canopy plants as ‘natural,’ as hurricanes and wildfire, human activities are increasing the severity and frequency of those in the USA and around the world.”

Ecological disturbances 

For her study, Nadkarni reviewed 255 previously published papers on ecological disturbances affecting epiphytes across 58 countries. 

The analysis revealed that forest fragmentation was the most frequently cited disturbance to epiphytes, followed by climate change, harvesting, and extreme events.

“Across all impacts, disturbance agents were significantly more likely to lead to negative, rather than positive, effects in both tropical and temperate locales,” wrote Nadkarni.

Keystone roles

“Communities of plants that live in rainforest canopies – ferns, orchids and bromeliads – play ‘keystone roles’ in maintaining biodiversity, fostering critical interactions for pollination and seed dispersal and maintaining healthy nutrient cycles, even though their biomass is small relative to whole forests,” explained Nadkarni. 

“Many of them have been cultivated by people for centuries because of their beauty and the ways they connect us to aesthetically and spiritually to nature.”

Intercepting nutrients

In a 2009 TED talk, Nadkarni passionately spoke about these plants, explaining how they absorb nutrients from mist and fog through their leaves. 

“They don’t have roots that go into trunks or to the forest floor, but rather it is their leaves that are adapted to intercept the dissolved nutrients that come to them in the form of mist and fog,” Nadkarni said.

“Underneath these live epiphytes, as they die and decompose, they actually construct an arboreal soil…They have a tremendous capacity for holding onto nutrients and water.”

“If you pull back on those mats of epiphytes, what you’ll find underneath them are connections, networks of what we call canopy roots. These are not epiphyte roots. These are roots that emerged from the trunks and branches of the host trees themselves.” 

“And so those epiphytes are actually paying the landlord a bit of rent in exchange for being supported high above the forest floor.”

Implications for the future of Epiphytes

To protect these vital plants, Nadkarni recommends actions like retaining old, large trees during forestry activities, harvesting epiphytes from only limited areas, and safeguarding vast forest sections. 

Nadkarni concluded that it is imperative to share these insights with policymakers and land managers. Collaborative efforts are needed to shield epiphytes from harm.

The study is published in the journal New Phytologist.

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