The Fruits of Civilization (72-6-4) Vines


Vines can change forests in a lot of ways. They hit big, slow-growing trees far harder than smaller, faster-growing species, meaning they can probably change the entire composition of the forest. ~ American ecologist Stefan Schnitzer

Forests look idyllic, but the appearance of tranquility is belied by vegetation in constant conflict. The ancient battle between trees and vines is especially embittered.

If the forest was a financial system, trees would be old money: their deep roots, stout wood, and slow growth represent a long-held investment. These guardians of the woodlands are home to a zoo of species, just as coral reefs create an ecosystem all their own.

Conversely, vines are fleeting speculators: agile and aggressive competitors. Vines spend little in supportive tissue. Instead, they take advantage of trees’ capital stock, scrambling up trunks to the canopy, where they produce a flush of leaves and brazenly bask in the beaming sunshine at the top of the forest.

Climbers comprise up to half of the plant species in a typical rainforest. Vines produce 40% of the leaves. Long-stemmed woody vines (lianas) can grow to hundreds of meters long.

Trees pay a high price for the presence of lianas: the vines strangle and deform tree branches. Their dense foliage deprives trees of sunlight. Vine roots scoff water and nutrients. Trees bearing vines grow more slowly, reproduce less, and die earlier than those without.

Once lianas reach the canopy, they spread out, effectively roping trees together. If a tree falls, those nearby connected by vines can be dragged down.

Light-loving vines increase rapidly in forests fragmented for agriculture or by selective logging. Small 2nd-growth trees on the edge of disturbed forests are ideal trellises for rapid ascent to the canopy. Trees here die 2 to 3 times more quickly.

Humans have introduced invasive vine species that have wreaked havoc, as kudzu in the southeastern US and the rubber vine in northern Australia illustrate.

The time is ripe for vines, which are proliferating in forests undisturbed. This is the result of climate change.

Global warming and changes in weather patterns, along with rising atmospheric CO2, have upped the tempo of forest life. Faster plant growth intensifies competition, which drives more rapid turnover. All these factors favor vines.

Climbers make life tough for more than trees. Plants that live on trees, such as ferns, are excluded with dense vinery. Ferns act as islands of biodiversity, sustaining numerous arboreal animals.

Vines likely contribute a positive feedback to global warming from CO2 release. Trees store carbon in their tissues. When trees come a cropper from climbers, some of that carbon is released into the atmosphere.