The Perilous Plight of Rainforest Epiphytes – PNAS (2024)

Epiphytes (mosses, ferns, bromeliads and orchids) are a strikingly interesting group of non-parasitic plants prevalent in the tropics that live on the surface of other plants. They are particularly abundant and diverse in mountainous cloud forests. Epiphytes are interesting because they constitute an important part of nutrient cycle in their ecosystems capturing moisture and nutrients from the air. In the tropics they can accumulate a considerable amount of biomass within forest canopies and form a special type of micro environment for a whole suit of organisms. However, Human driven climate change is affecting the self-sustaining properties of tropical forests and there is a growing trend that lowland rainforests are progressively experiencing longer dry seasons . The drought experienced in the Amazon in 2023 was especially alarming. Many sections of the Negro River reached lowest levels in 120 years, when measurements began. Tropical forests along altitudinal gradients are also being affected in that certain wet zones become compressed when climate change raises the cloud base. Epiphytic plants which are dependent on cloud immersion in the canopy are adversely affected. The way epiphytes intercept microdroplets in a cloud forest is quite unique. The wicking effect they cause facilitates a slow through-flow outside of the branches and trunks. The decline of epiphytes may trigger a cascade of effects for the whole forest water cycle.

Epiphytes are sensitive to atmospheric fluctuations and therefore are considered good indicator species for monitoring the effects of climate change in tropical ecosystems. To investigate researchers use diverse methods involving climbing into the trees.