Bubbles that kill

Kate Heaphy

Trees draw water taut,
straining skyward in
continuous columns that
defeat gravity.
From root to stomata,
tension in perfect balance –
until

The cup empties.
Internal straws collapse,
gargling thin air.
Parched owners silent,
cheeks hollow.
With tension interrupted, 
Leaves wilt, blood clots –
embolism

In silence, we mirror them.
Few turn, fewer speak,
too busy inside
our own insidious bubbles.
How dare their thirst
intrude on ours!
An imaginary film shields us
from such distant tensions –
until

Canopy cover thins,
flying rivers still.
A carbon bomb ticks as
fires blaze uncontrolled.
Complex communities collapse,
spiralling down, down,
towards savannisation.
Around the world, buzzwords gurgle:
ecosystem services, tipping points.
Surface tension ruptures –
the bubble bursts.

And nothing rises.

The Science

The Amazon forest faces multiple pressures, including climate change, wildfires, and deforestation, which are placing growing tension on the system. The increasing frequency and severity of drought due to climate change not only threatens individual trees, but also pushes the entire ecosystem towards a tipping point. Beyond this threshold, parts of the forest could shift toward drier, more savannah-like states and lose their capacity for crucial “ecosystem services” such as carbon storage and water cycling, further amplifying climate change.

Inside a tree, negative pressure builds in the water transport tubes of plants (xylem) when water is limited. If this tension becomes too great, air bubbles (embolisms) form in the xylem and break the water column, increasing vulnerability to other pressures and likelihood of mortality. Scientists often measure a tree’s drought resilience by its P50 value, an analogous threshold where half of a plant’s water transport capacity is lost and the chance of recovery decreases.

The parallel between scales is striking. Both individual trees and the mighty Amazon forest will collapse if the tensions that are stretching each system’s limits become too great. Preventing rupture requires urgently reducing climate change impacts by halting deforestation and reducing global greenhouse gas emissions.

The Poet

Kate Heaphy is a conservation ecologist from New Zealand with a passion for storytelling. Over the past decade, she has worked in various environmental roles from contracting to consulting to research. She holds degrees across the natural and physical sciences and is currently working towards a PhD at Bangor University in Wales, where she is investigating drought responses of the Amazon forest. Kate writes poetry and historical fiction, and loves creative ways of communicating science.

Next poem: ceiiinosssttuv by Martin Zarrop