A new paper in Remote
Sensing of Environment shows that global vegetation reached a record high
in 2020. The increase in vegetation is due to increased CO2 in the atmosphere
which aids plant growth. While the overall effects of increased atmospheric CO2
are decidedly negative, there are some important positive effects that need to
be considered. One might ask the question that if we were able to decrease
atmospheric CO2 to 350ppm or even lower as many activists advocate, what would
the effects be on plant growth and food production? There is little doubt that
the effects would be negative. I wrote about global
greening in 2023. I noted then that NASA satellite data indicated that a
quarter to a half of Earth’s vegetated lands have had increases in leaf volume
on trees and other plants since 1980 and more is expected as atmospheric CO2
continues to rise. It is hard to argue that drawing down atmospheric CO2 won’t
be catastrophic for food production. The evidence suggests that it could be. In
the past, we never had to grow so much food because we had a much smaller
population. Fossil fuels, with all their detriments, have enabled us to
increase our population and have also enabled us to produce more food to feed
that population.
For the study, researchers,
led by Yulong Zhang from Duke University, analyzed satellite data from 2001 to
2020. The study utilized machine learning and ecological simulations. The
researchers attributed the positive changes to CO2, global warming, and
reforestation efforts.
They found that temperate and cold regions,
including boreal forests, benefited the most from global warming extending
growing seasons. More tree planting and better agricultural management in China
and India. The more modest greening increases
in tropical regions were attributed mainly to increased local rainfall.
Plants absorb CO2
through photosynthesis. They also contribute to atmospheric moisture through
transpiration, which aids cloud formation and precipitation regulation. The
researchers used the Leaf Area Index to quantify vegetation. Techno-Science explains:
“The Leaf Area Index (LAI) is a measure used to quantify
vegetation density. It represents the total leaf surface area per unit of
ground area, thus providing an indication of the amount of vegetation present
in a given area.”
The researchers advocate
for more and better vegetation monitoring, arguing in the paper’s abstract
below that there is a need for a better understanding of the year-to-year changes
in greening since there is great year-to-year variability. There is a need to
better quantify each variable’s influence on global greening. In addition to
LAI, the researchers utilized other remote sensing data including Enhanced
Vegetation Index (EVI) and Solar-Induced Fluorescence (SIF) as indicated below.
“To evaluate global greening status, we utilized three
groups of remote sensing-based vegetation indices (VI), including Enhanced
Vegetation Index (EVI), Solar-induced Fluorescence (SIF) and leaf area index
(LAI). EVI is designed to enhance vegetation signals in high biomass regions
while reduce soil and atmospheric background influences (Huete et al., 2002),
making it especially effective in areas where traditional indices like
normalized difference vegetation index may saturate and fail to…{sorry, it
was a snipett}.
Abstract
Terrestrial vegetation is a crucial component of Earth's
biosphere, regulating global carbon and water cycles and contributing to human
welfare. Despite an overall greening trend, terrestrial vegetation exhibits a
significant inter-annual variability. The mechanisms driving this variability,
particularly those related to climatic and anthropogenic factors, remain poorly
understood, which hampers our ability to project the long-term sustainability
of ecosystem services. Here, by leveraging diverse remote sensing measurements,
we pinpointed 2020 as a historic landmark, registering as the greenest year in
modern satellite records from 2001 to 2020. Using ensemble machine learning and
Earth system models, we found this exceptional greening primarily stemmed from
consistent growth in boreal and temperate vegetation, attributed to rising CO2
levels, climate warming, and reforestation efforts, alongside a transient
tropical green-up linked to the enhanced rainfall. Contrary to expectations,
the COVID-19 pandemic lockdowns had a limited impact on this global greening
anomaly. Our findings highlight the resilience and dynamic nature of global
vegetation in response to diverse climatic and anthropogenic influences,
offering valuable insights for optimizing ecosystem management and informing
climate mitigation strategies.
The study
utilized remote sensing via satellite, machine learning, and Earth system
modeling.
The researchers also
noted that the overall trend since 2000 was one of increasing greening, noting:
“…a long-term greening trend since the early 2000s (Piao
et al., 2020). This consistent pattern suggests a robust resilience and
adaptability of global vegetation.”
They also noted that the 2020 peak was mostly due to
tropical rainfall increases but also that the temperate and boreal increases
are more long-term, continuous, and more associated with atmospheric CO2 increases.
I will end this
post the same way I ended my previous post on the subject:
‘So, like it or not, higher atmospheric CO2 and a bit of
warming leading to slightly longer growing seasons probably do allow us to
produce more food.’
References:
Earth
greener than ever in 2020: an ecological surprise. Adrien. Techno-Science,net.
February 19, 2025. Earth
greener than ever in 2020: an ecological surprise 🌿
Earth's
record-high greenness and its attributions in 2020. Yulong Zhang, Jiafu Mao, Ge
Sun, Qinfeng Guo, Jeffrey Atkins, Wenhong Li, Mingzhou Jin, Conghe Song, Jingfeng
Xiao, Taehee Hwang, Tong Qiu, Lin Meng, Daniel M. Ricciuto, Xiaoying Shi, Xing
Li, Peter Thornton, and Forrest Hoffman. Remote Sensing of Environment. Volume
316, 1 January 2025, 114494. Earth's
record-high greenness and its attributions in 2020 - ScienceDirect
No comments:
Post a Comment