Science

A plant’s-eye view of the climate reveals weird new ecosystems

The conditions for plant survival and growth are going to change: we need to help them adapt

An old oak tree in Cahermurphy Oak Wood, a hyper-oceanic temperate rain forest remnant in the the Slieve Aughty mountain range of East Clare and South Galway. Photograph: Bryan O’Brien

Yvonne Buckley
Thu Apr 25 2024 - 07:00

Plants are the ultimate in climate detectors. The temperature and rainfall of a region, how many frost days per year occur, and how variable the seasons are, determine what kinds of plants can occur in a particular climate. Indeed, all the world’s climatic zones can be classified according to how suitable they are for particular kinds of plants: a plant’s-eye view of the planet.

Although there are more than 391,000 species of vascular plants, this mind-blowing complexity can be simplified into just 14 different plant “growth forms”. From a plant’s perspective the world is divided not into countries and regions with political boundaries, but into places that are more or less suitable for being a tree, or succulent, or grass. Some places are the kingdoms of towering evergreen trees, others are suitable only for hardy grasses and cacti.

A team of German and Swiss scientists have mapped the world’s climate from a plant’s perspective and have used climate and plant growth models to predict how plants’ view of climate will shift with climate change.

From a plant’s perspective, Ireland’s climate is particularly suitable for deciduous trees and shrubs that like a cold climate, needle-leaved trees such as pine, cool temperature-loving grasses, and herbs. In contrast, the tropical climate of countries such as the Democratic Republic of the Congo or Ecuador are perfect for evergreen trees and climbing plants, the archetypal rainforest.

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As the climate changes, the boundaries of these plant domains are predicted to shift. Plant perceptions of change differ from purely climatic descriptors. For example, while the hot arid desert of the Sahara is predicted to become even hotter, this has little impact on plant life as much of the desert is already of low suitability for plants.

In contrast, changes to the temperature of polar regions make the grassy tundra much more suitable for trees and shrubs, pushing the remaining tundra vegetation on to the very northernmost edge of the Arctic. The impact of changing climate on plants depends not just on how the climate changes but where that change starts from and the other limiting factors for plants, like nutrients.

Many future climatic zones will remain suitable for plant life in general, and have the same kinds of suitability for different plant life forms that exist today. However, where these conditions will occur will change and there are some places on Earth that are predicted to have a climate that, from a plant’s perspective, will have no modern-day comparator.

These novel plant-climates will occur in southeastern South America and Australia. These places transform from being suitable for a wide range of plant growth forms to being suitable largely for types of plants that do not currently commonly occur together, conditions suitable for weird new ecosystems.

There are some combinations of future climate conditions that will result in the complete global disappearance of current plant-climates. The species that currently occupy these plant-climates are at high risk of disappearing as well. If the climate becomes unsuitable for the unique collection of interacting species in these disappearing plant-climates conservation and restoration face an uphill, if not impossible, battle.

Given the large, predicted shifts in plant-climates over the next 50 years, what can be done to mitigate and adapt to these changes? Reductions in greenhouse gas emissions from our current damaging pathway will significantly lessen the disruption to plant-climates. Climate change mitigation actions are therefore critical for protecting biodiversity and enabling ecosystems to adapt to changing climate.

Conservation and restoration actions across whole landscapes, which provide conditions suitable for plant species to track suitable climates, are also essential and conserving small isolated patches will become increasingly difficult. Ecologists need to start predicting not just where suitable plant-climates might occur, but how reassembly of plant communities in changing conditions might happen and how weird novel plant-climates and ecosystems might function.

[ How bad is Irish nature loss and can we turn the tide? ]

Effects of climate on humans depends on the plant’s-eye view of the world. The contributions that plants make to our survival and wellbeing rely on functioning of diverse ecosystems in many different climate conditions. As the conditions for plant survival and growth start to be reshuffled, plants will need our help to persist, track and reassemble in the new climates.

Prof Yvonne Buckley is the co-director of the Co-Centre for Climate + Biodiversity + Water based in Trinity College Dublin

BiodiversityClimate changeTrinity College Dublin (TCD)