Plants struggle to keep pace with climate change in human-dominated
landscapes

Date:
December 7, 2021
Source:
University of California - Santa Cruz
Summary:
Researchers found that changes in plant phenology are lagging
behind rising temperatures across a majority of the Northern
Hemisphere, particularly in the most human-dominated landscapes,
like crop lands.



FULL STORY ========================================================================== Researchers at UC Santa Cruz are contributing new insights into the
challenges plants face in adapting to climate change. Prior research
has long anticipated that plants might be able to respond to increasing temperatures by changing their phenology -- or the timing of seasonal
life processes -- at a rate that matches the rate of climate change. But
a new global-scale analysis, published in the journal AGU Advances,
shows that phenological changes are lagging temperature change, and this
trend seems to be more pronounced in human- dominated landscapes.


==========================================================================
"We would commonly expect phenology to adapt very quickly to climate
change, but with these findings, we see that there's probably a limit
to how much adaptation we can see, and this limit is affected by human activities," said Yiluan Song, a UCSC Ph.D. student in environmental
studies and lead author of the paper. "These findings open up a lot
of questions to explore in terms of our expected response of plants to
climate change." To arrive at their findings, the research team -- under
the guidance of UCSC Associate Professor of Environmental Studies Kai
Zhu -- focused on the Northern Hemisphere at mid- to high- latitudes and analyzed satellite remote-sensing data that detects the warm-season growth
of plants on the ground. Growing seasons in the Northern Hemisphere are generally expected to start earlier and last longer as average annual temperatures increase. But in comparing the rate of change for both
factors geographically, the paper identified a spatial mismatch.

According to the analysis, between 1981 and 2014, the length of the
growing season has changed slower than the average annual near-surface temperature across a majority of the Northern Hemisphere. And in some
areas, these changes were even moving in the opposite direction, with
growing seasons compressing when they were expected to lengthen. There
was a high degree of variability across the study region, but these
trends were especially prominent in Europe and parts of North America.

Researchers are working to understand why this mismatch between
growing season phenology and temperature change might be occurring. One possibility is that the rate of temperature change may simply be too great
for plant phenology to adequately keep up. Prior research also shows that plants may be limited by their need to respond to other environmental
variables too -- like the length of the day and precipitation -- and
that the species types and compositions of plant communities across
parts of the Northern Hemisphere may shape phenological response. But
the new study also points to another key variable: human activity.

Song and the research team layered their findings of phenological mismatch
with data on human population density and land-use types across the study
area. This analysis revealed that phenological mismatch corresponded
with human population density across latitudes. And the effect was more pronounced in the most human- dominated landscapes, especially croplands.



==========================================================================
Over the whole study area, the larger trend of lag or divergence in phenological changes across human-impacted landscapes offset a trend
where phenological shifts were actually ahead of temperature changes in wildland areas. The team supported their findings with additional data
from on-the- ground observations by citizen scientists. This analysis
showed that the mismatch between temperature-related environmental
conditions and the timing of initial growth of spring leaves increased
with human population density.

The paper's authors hope their findings might help to inform new
approaches in the study of plant phenology.

"While plant phenology has been well-researched, conventional approaches
focus on natural systems -- looking at forests or grasslands and
intentionally excluding the areas with human dominance," explained Kai
Zhu, senior author of the paper. "But we are in the Anthropocene. When you
look at the land across the earth, a large chunk of it has been modified
by humans, and I think this study shows that it would be a mistake to
not account for that." Zhu said studying phenology across all land-use
types could help to build a more comprehensive understanding of the role
plants play in the climate system, which also affects the projections
produced by climate change models and resulting management plans.

"We particularly want to know more about the implications of these
new findings on the carbon cycle," he said. "Plants are currently
doing us a great service in taking up a lot of the carbon emissions
we put into the atmosphere, but the length of the growing season is an important factor that determines how much carbon they can sequester."
In agricultural settings, warming can accelerate crop development,
leading to an early harvest, but adaptive management practices could
better match plant phenology with climate conditions to take advantage
of longer growing seasons.

Additional research will be needed to understand how human activities --
like irrigation, selective planting, or land disturbance -- might affect climate- phenology coupling and what the long-term impacts of this effect
could be.

Overall, the paper's authors argue that maintaining a stable relationship between climate and plant phenology is crucial for maintaining both
biological diversity and ecosystem productivity into the future. And
the more scientists can learn about the factors affecting phenological responses, the better prepared society will be to manage ecosystems productively.

"We anticipate that the degree of mismatch may ultimately depend
on how humans intervene," Zhu said. "If we are smart enough,
I think we could probably be adaptive to climate change through
better management of plants. We are still learning in that process." ========================================================================== Story Source: Materials provided by
University_of_California_-_Santa_Cruz. Original written by Allison
Arteaga Soergel. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Yiluan Song, Christopher J. Zajic, Taehee Hwang, Christopher R.

Hakkenberg, Kai Zhu. Widespread Mismatch Between Phenology and
Climate in Human‐Dominated Landscapes. AGU Advances, 2021;
2 (4) DOI: 10.1029/ 2021AV000431 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/12/211207152621.htm

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