Plants may run out of time to grow under ongoing climate change
EMBARGO: 10th June 2015, 11am Pacific/2pm Eastern
The causes and consequences of global warming are still under debate, but what would
actually happen to all the plants, essential to many aspects of our lives, if the climate in
the planet does get warmer? A new study publishing in the Open Access journal PLOS
Biology on June 10th by University of Hawai‘i scientists addresses just this question.
A key potential ‘benefit’ of global warming that has been considered is that plants at
northern latitudes will thrive in a warmer world. However, this prevailing assumption
ignores the fact that plants in the North will remain limited by solar radiation, curbing the
positive effects of warming and additional CO2 availability. In addition, that same
warming could surpass plant temperature tolerances in tropical areas around the world,
and further be accompanied by drought.
“Those that think climate change will benefit plants need to see the light, literally and
figuratively,” says Camilo Mora, professor at the University of Hawai‘i at Mānoa’s
College of Social Sciences and lead author of the new study. “A narrow focus on the
factors that influence plant growth has led to major underestimations of the potential
impacts of climate change on plants, not only at higher latitudes but more severely in the
tropics, exposing the world to dire consequences,” he adds.
The new study shows that ongoing climate change will lead to overall declines in plant
growing days by 2100 due to a mixture of warming, drought, and limited solar radiation.
Using satellite-derived data, the study identified the ranges of temperatures, soil
moisture (water availability) and light (solar radiation) within which 95% of the world’s
plant growth occurs today. The researchers then used climate projections to count the
number of days in a year that will fall within these suitable climate ranges for plant
growth in the future.
Although the study did find that warming trends will increase the number of days above
freezing at higher latitudes by 7%, these same locations will remain limited by light, a
trend that has been missed by previous studies that focused on temperature alone.
“Regions at higher latitudes will likely have less frost and snow on the ground in the
future, but many plants will not be able to take advantage of those warmer temperatures
because there will not be enough sunlight to sustain their growth,” says Iain Caldwell, a
co-author of the study.
The same warming that appeared to be a positive influence on plant growth at higher
latitudes was found to be detrimental to plants in tropical regions, where conditions will
become too warm and dry for most plant growth. Overall, the entire planet could see
~11% reduction in the number of days with suitable climates for plant growth, with some
tropical regions facing a reduction of up to 200 days per year by 2100.
“Although plants that have already adapted to live in extreme hot and dry conditions
could fare well under a warming planet, the challenge will be for tropical agricultural and
forest ecosystems to adapt to conditions that will likely surpass what they can currently
tolerate,” says Jamie Caldwell, another co-author.
Plants also sustain human societies by providing food, fiber, fuel, jobs and associated
revenue. However, they can only deliver those things when climates are suitable for their
growth.
The new study goes further to assess where people will be hardest hit by the changes in
the number of plant growing days. While some northern regions – predominantly in
China, Russia and Canada – will likely experience improved climatic conditions for plant
growth, approximately 2.1 billion individuals are highly vulnerable to the projected
changes. These 2.1 billion people currently live in countries that depend heavily on
plants for food, jobs and revenue, and have minimal capacity to adapt because they are
poor, yet they could lose 30% or more of their current plant-growing period.
“Climate change will have disproportional impacts on the poorest in the world,” says
Micah Fisher, another co-author of the study. "Our analysis showed, for example,
dramatic potential human impacts on the Sahel and on certain pacific islands. If
subsistence farmers in the Sahel lose half of their growing days for plant crops, it will be
hard for them to feed their families".
On a more positive note, changes in suitable plant growing days were negligible under
strong and moderate mitigation scenarios, suggesting that even modest reductions in
emissions could prevent such drastic changes and their associated consequences for
ecosystems and people.
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Contact:
Dr. Camilo Mora, +011- country code (57), area code (320) phone number (693 4305);
cmora@hawaii.edu; (available from Colombia)
Dr. Iain R. Caldwell, irc@hawaii.edu; (available from Hawai‘i)
Jamie M. Caldwell, +1-808-236-7424; jsziklay@hawaii.edu; (available from Hawai‘i)
Micah Fisher, +011- country code (62), city code (812) phone number (12154828)
micahrf@hawaii.edu; (available from Indonesia)
Citation: Mora C, Caldwell IR, Caldwell JM, Fisher MR, Genco BM, Running SW (2015)
Suitable Days for Plant Growth Disappear under Projected Climate Change: Potential
Human and Biotic Vulnerability. PLoS Biol 13(6): e1002167.
doi:10.1371/journal.pbio.1002167
Funding: This paper was funded by a grant/cooperative agreement from the National
Oceanic and Atmospheric Administration, Project R/IR-31, which is sponsored by the
University of Hawaii Sea Grant College Program, SOEST, under Institutional Grant No.
NA14OAR4170071 from NOAA Office of
Sea Grant, Department of Commerce. The funders had no role in study design, data
collection and analysis, decision to publish, or preparation of the manuscript.
Competing Interests: The authors have declared that no competing interests exist. The
views expressed herein are those of the authors and do not necessarily reflect the views
of NOAA or any of its sub-agencies. UNIHI-SEAGRANT-JC-14-35.
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