ArticlePDF Available

Biogeochemistry: Taking stock of forest carbon

Authors:
Peter B Reich at University of Minnesota
Peter B Reich
Download full-text PDF
Read full-text
Download citation

Abstract and Figures

Forests take up and store large quantities of carbon. An analysis of inventory data from across the globe suggests that temperate and boreal forests accounted for the majority of the terrestrial carbon sink over the past two decades.
Figures - uploaded by Peter B Reich
Author content
All figure content in this area was uploaded by Peter B Reich
Content may be subject to copyright.
Content uploaded by Peter B Reich
Author content
All content in this area was uploaded by Peter B Reich on Dec 28, 2015
Content may be subject to copyright.
346 NATURE CLIMATE CHANGE | VOL 1 | OCTOBER 2011 | www.nature.com/natureclimatechange
news & views
Imagine a tree trunk, tens of metres tall,
lying across the forest oor. Now image
you and two dozen, better three dozen,
friends, liing it by hand. erein lies the
signicance of trees and forests when it
comes to carbon sequestration; trees are
heavy, and carbon accounts for almost half
their dry weight. Forests are an important
net carbon sink globally: each year they
remove more carbon from the atmosphere
by photosynthesis than they return via
all processes, including respiration and
deforestation. e exact magnitude of this
global forest carbon sink is dicult to gauge,
but is thought to lie between 2.0and 3.4Pg
of carbon per year for intact forests. Now,
writing in Science, Pan and colleagues1
use forest inventory data to estimate the
magnitude of the forest carbon sink over
the past two decades, in what is probably
the most up-to-date and thorough study of
itskind.
e forest carbon sink has been
estimated using several approaches, each
with its own strengths and weaknesses.
Global vegetation models have been used to
determine the size of the land carbon sink,
as have mass balance methods, which rely
on estimates of oceanic and atmospheric
sinks, and inverse modelling techniques,
which rely on measurements of the
concentration and geospatial distribution of
carbon dioxide2,3.
Pan and colleagues1 use yet another
approach to assess forest carbon stocks and
uxes across the globe between 1990and
2007; one that is reliant on forest-inventory
and land-cover data, ancillary data and
estimates. e simplicity of the approach
undoubtedly belies the Herculean eort
involved: they assessed the carbon content of
live biomass, dead wood, litter, soil organic
matter and harvested wood products in
tropical, temperate and boreal forests, and
examined how these stocks changed over
time. According to their analysis, intact
forests and those re-growing following
disturbance sequestered around 4Pg C yr−1
over the measurement period — equivalent
to around 60% of emissions from fossil fuel
burning and cement production combined.
is gross sequestration number sounds
more favourable than it is though, as
tropical deforestation resulted in the release
of almost 3Pg C yr−1. us, globally, the
net forest carbon sink (counting all gains
and losses, including from deforestation)
amounted to just 1.1Pg C yr−1, or one
seventh of emissions from fossil fuel and
cement production (Fig.1), in line with
previous estimates. Furthermore, the net
forest carbon sink from forests remaining
intact — a number given emphasis in
previous scientic assessments — was
2.4PgC yr−1, in the middle of the range of
previous estimates1,2.
e contribution of tropical, temperate
and boreal biomes to the forest carbon sink
was also explored. In the tropics, re-growth
of cleared and logged forests, and continued
growth of intact tropical forests, generated a
colossal carbon sink of 2.83Pg C yr−1, which
largely, but not entirely, counterbalanced
emissions associated with deforestation. As a
result, the tropics served as a relatively small
net source of carbon to the atmosphere
BIOGEOCHEMISTRY
Taking stock of forest carbon
Forests take up and store large quantities of carbon. An analysis of inventory data from across the globe suggests
that temperate and boreal forests accounted for the majority of the terrestrial carbon sink over the past
two decades.
Peter B. Reich
4
2
0
–2
–4
–6
–8
Pg C yr–1
Anthropogenic
emissions
Temperate
forests
Boreal
forests
Tropical
source
Tropical
sink
Tropical
forests
Carbon sink/source
Figure 1 | The global forest carbon sink. Pan and colleagues1 used forest inventory data to show that
temperate and boreal forests comprised 100% of the net forest carbon sink between 1990and 2007.
Despite the gross sequestration of large quantities of carbon, tropical forests served as a small net source
of carbon to the atmosphere (dark green bar), due to the even larger losses of carbon dioxide associated
with deforestation. The error bars represent estimated uncertainties based on a combination of
quantitative methods and expert opinion. The uncertainty associated with the net tropical carbon balance
is not known. Anthropogenic emissions and forest carbon data, and uncertainty, taken from ref.1. Image
credits (from left): 1,2, © iStockphoto.com/bronswerk/raciro; 3,4, © Getty Images.
© 2011 Macmillan Publishers Limited. All rights reserved
NATURE CLIMATE CHANGE | VOL 1 | OCTOBER 2011 | www.nature.com/natureclimatechange 347
news & views
over the measurement period (Fig.1). In
contrast, temperate and boreal forests —
which together accounted for much less
than half of the global gross forest carbon
uptake— were responsible for the entire net
forest carbon sink (Fig.1).
e magnitude of the carbon sinks
and sources in the tropics suggests that
tropical forests are key to future carbon
cycling. Pan and co-workers suggest that,
if managed appropriately, tropical forests
could serve as a large net sink of carbon in
the future and make the United Nation’s
Reducing Emissions from Deforestation and
Forest Degradation (REDD) programme
a meaningful contributor to osetting
emissions. Conversely, if deforestation were
to continue unabated, and disturbance
from land-use, drought, re and climate
were to grow this century, as seems likely,
then tropical forests could become a large
net source of carbon to the atmosphere,
with serious consequences for the global
climatesystem.
Of course, the uncertainties associated
with their estimates of carbon-sink size
are signicant. In attempting to estimate
global pools of carbon in forests in all forms,
numerous assumptions were used. Even
in countries with the most sophisticated
forest inventories — largely developed
nations in Europe and North America —
insucient coverage of all forest sectors,
together with errors in accounting, mean
that large uncertainties are evident at the
national scale. As a result, the magnitude of
the uncertainty associated with the global
carbon sink is large and nearly matches that
of the sink itself.
More important than these uncertainties,
perhaps, is the question of whether the
current sink strength of the world’s forests
will persist over the next 25to 50years.
ere are many reasons why it might not,
including warming-induced emissions from
boreal forests, heightened deforestation
in the tropics, and a reduction in the
fertilization eect of increased levels of
carbon dioxide, as other resources, such as
nutrients and water, become proportionally
more limiting4–7.
Furthermore, forests inuence climate
in numerous other ways, aside from
carbon cycling. Forests emit greenhouse
gases other than carbon dioxide, such as
nitrous oxide and methane8, and oen
reduce the reectivity of the Earth’s surface
by absorbing solar radiation9. Although
both of these processes act to increase
radiative forcing, their impact on future
climate will depend on variables such as
land use, forest management and human
disturbance. For example, shis in land
management that alter the extent and
timing of soil waterlogging may inuence
trace-gas emissions, and shis in forest
management towards species that dier in
spectral qualities could inuence albedo9,10.
Although dicult to quantify on a global
stage, these additional emissions and
biogeophysical eects need to be considered
when assessing the role of forests in the
climate system.
e ndings of Pan and colleagues1
demonstrate the ongoing importance of
forests as a key carbon sink. Unfortunately,
however, they do not provide a road map
to the future. Whether the carbon-sink
strength of the world’s forests will shi
this century, and whether emissions of
greenhouse gases (other than carbon
dioxide) and shis in surface reectivity will
act to dampen or amplifyanthropogenic
warming, remains to be seen. ❐
Peter B. Reich is at the Department of Forest
Resources, University of Minnesota, St Paul,
Minnesota 55108, USA, and the Hawkesbury
Institute for the Environment, University of Sydney,
News South Wales, Australia.
e-mail: preich@umn.edu
References
1. Pan, Y. etal. Science 333, 988–993 (2011).
2. Le Quere, C., Raupach, M.R., Canadell, J.G., Marland, G. et al.
Nature Geosci. 2, 831–836 (2009).
3. Nassar, R. etal. Atmos. Chem. Phys. 11, 6029–6047 (2011).
4. Lewis, S.L., Lloyd, J., Sitch, S., Mitchard, E.T.A & Laurance, W.F.
Annu. Rev. Ecol. Syst. 40, 529–549 (2009).
5. Zhao, M. & Running, S.W. Science 329, 940–943 (2010).
6. Kurz, W.A., Stinson, G., Rampley, G.J., Dymond, C.C. &
Neilson, E.T. Proc. Natl Acad. Sci .USA 105, 1551–1555 (2008).
7. Reich, P.B., Hungate, B.A. & Luo, Y. Annu. Rev. Ecol. Syst.
37, 611–636 (2006).
8. Van Groenigen, K.J., Osenberg, C.W. & Hungate, B.A. Nature
475, 214–216 (2011).
9. Betts, R.A. Nature 408, 187–190 (2000).
10. Ollinger, S.V. etal. Proc. Natl Acad. Sci .USA
105, 19336–19341 (2008).
It is no longer news that China, with its
unprecedented economic development,
has become one of the world’s biggest
energy consumers and, therefore, one of
the world’s largest carbon dioxide emitters.
e international debate around the
magnitude and trend of China’s carbon
footprint has spurred research on the issue
and encouraged the Chinese government to
take on measures to address climate change.
Fair and eective national abatement eorts
should reect the dierences in regional
contributions to China’s carbon dioxide
emission levels. However, little is known
about the dierent regional emission paths
behind China’s carbon footprint. Chinese
regions show very diverse economic
conditions, with highly developed areas
relying on state-of-the-art technologies and
others still under-developed depending on
old infrastructure and technologies. e
level and trend of their carbon emissions
vary substantially, but the dierences are
not captured in an aggregate indicator such
as the national carbon footprint. Writing
in Energy Policy, Meng and colleagues1
highlight the great disparities in regional
emission patterns in China and show
how these dierences are important for
climatepolicy.
anks to remarkable economic growth
over the past three decades, China’s
domestic living standards have been
greatly enhanced, and between 1981and
2005 about 600million people2 were
lied out of poverty. Nevertheless, China’s
economic wonder has come at a high
price. Owing to the huge consumption
of fossil fuels, especially coal, to meet its
increasing demand for energy, China’s
natural environment has deteriorated
rapidly. Increased levels of air and water
pollution endanger people’s health, and
extreme weather events have increased in
scale and frequency presenting a growing
threat to the population. e Chinese
government has realized the need to tackle
these environmental problems and, in
POLICY
China’s regional emissions
The reduction of carbon dioxide emissions is a pressing challenge for China. Now research demonstrates that China’s
local energy-related emission patterns are important for setting eective greenhouse-gas abatement policies.
Yongfu Huang and Jingjing He
© 2011 Macmillan Publishers Limited. All rights reserved
... In addition to being one of the most biologically diverse terrestrial environments (DeAngelis 2008, FAO 2010, forests also play a crucial role in climate change mitigation. For example, recent estimates suggest that forests absorb one-third of annual carbon dioxide emissions released from fossil fuels and contributing to a healthy atmospheric balance of oxygen, carbon dioxide and humidity (Reich 2011). Furthermore, more than 1.6 billion people rely on forests for their daily subsistence needs (Ghimire and Pimbert 1997). ...
... In addition to being some of the most biologically diverse terrestrial environments (DeAngelis 2008, FAO 2010), more than 1.6 billion people rely on forests for their daily subsistence needs (Ghimire and Pimbert 1997), and they also play a crucial role in climate change mitigation. Recent estimates suggest that forests absorb one-third of annual carbon dioxide emissions released from fossil fuels and contribute to a healthy atmospheric balance of oxygen, carbon dioxide and humidity (Reich 2011). ...
A transdisciplinary evaluation of forest retention policies and practices in the Australian context PhD
Thesis
Full-text available
  • Jun 2020
Environmental changes caused or influenced by human activity have increased the current rate of extinction to 100-1000 times the standard background rate (Ceballos et al. 2015). The reduction or loss of habitat for conversion to extractive uses, urban development or resource production causes environmental change and is considered a key threat to the suite of values associated with intact forests (Kingsford et al. 2009). Important mechanisms for abating species decline in the face of such pressures include protected areas and vegetation management policy. Globally, protected area expansion is exponential (Steffen et al. 2011) and yet studies that test the effectiveness of protected areas in achieving biodiversity outcomes remain rare (Schleicher, Eklund, D. Barnes, et al. 2019). This is highly problematic because a lack of evaluation undermines society’s ability to address emergent declines in biodiversity or ecological integrity, and to adapt policy responses accordingly. Commonly adopted targets relating to the simple area of a region or representation of species or communities, are easy to count for reporting purposes but may be achieved with little value in terms of avoiding the loss of biodiversity. As previous studies have shown, strict adherence to these targets without a deep understanding of ecological and conservation science may threaten bona fide progress in terrestrial conservation because resources for nature conservation are limited and increasingly disproportionate to the magnitude of biodiversity loss. It is of the utmost importance to effectively prioritise conservation policies and programs to maximise the efficiency of limited funding. A failure to maximise the efficacy of programs and policies is problematic not only in terms from a scientific perspective but also because failing to adequately control threatening processes can have a disastrous impact on biological diversity and ecological integrity. Effectively designing policies and programs requires a deep understanding of social, cultural, economic and political values. This thesis contributes to filling gaps in political and socio-economic values by evaluating the effectiveness of policy responses to deforestation in Australia, a global deforestation hotspot (Cresswell and Murphy 2017). The goals of this thesis are to: 1) review policies and programs for retaining natural forested habitats in Australia; 2) estimate the impact of current protected areas in terms of preventing forest cover loss; 3) describe the impact of policy changes on vegetation; 4) develop evidence-based recommendations for retaining Queensland’s forests in the future. Owing to complex governance arrangements for forest retention policies and programs, I use a transdisciplinary mixed-methods approach to investigate the complexities, effectiveness and future directions for conservation policy in Queensland, Australia. I combine rigorous qualitative policy analysis 2 (Chapters 2 and 4) with robust quasi-experimental evaluation methods (Chapters 3) and frequentist modelling (Chapter 5) to produce policy-ready recommendations for the future security of Queensland’s native forests (Chapter 6). In my first chapter, I set the scene for the relevance of this work by broadly introducing the primary mechanisms for forest retention (protected areas and environmental impact assessment). In developing this chapter, it became clear that the Australian state of Queensland is characterised by high rates of clearing, low rates of formal protection and globally significant biodiversity. These characteristics make Queensland an ideal case study for evaluating the effectiveness of deforestation mechanisms. To do this, however, there is a clear need to understand how protected areas are established across Australia. That is, what are the fundamental principles which drive gazettal. In Chapter 2, I use thematic analysis to identify and describe these principles as they occur in Australian policy documents. I found that representativeness was the most common driving principle for protected areas. Representativeness refers to ensuring that each type of ecosystem is contained within a reserve network. Given Queensland’s high rates of clearing (established in Chapter 1), however, is it logical to consider the feasibility of meeting a representativeness target as ecosystems are increasingly threatened with extinction. The next logical question, then, is whether or not protected areas effectively reduce clearing. The aim of Chapter 3 is to assess Queensland’s protected area network for impact retrospectively. This establishes counterfactual scenarios to provide a robust estimate of the relative impact of Queensland’s protected area system. I found that the majority (89.5%) of strictly protected areas would not have been cleared even in the absence of protection. This means that protection made no difference to deforestation in these areas. It is equally important to understand how regulation which relates to vegetation management contributes to de facto protection. An area is considered to be de facto protected if policy interventions prevent or significantly limit clearing. In this context, the relevant policies are guidelines which support Queensland’s Vegetation Management Act, 1999 (the Act). In Chapter 4, I evaluate the spatially explicit criteria for each guideline, summarise and then describe policy changes, including those which result in de facto protection. I found that the majority of Queensland’s vegetation does not have spatial features which would trigger an assessment under the Act. Australia’s significant and mostly endemic biodiversity is in long-term decline. The single most significant factor which can be attributed to continued species decline is habitat loss as humans increasingly modify natural environments. The results of the Chapters described above suggest that the mechanisms for retaining forested habitats in Queensland could be bolstered by understanding potential future scenarios of land clearing. These future scenarios can be a critical guide for strategic directions by anticipating opportunities to avoid the loss of high-risk areas. In Chapter 5, I used a generalised estimating equation to predict deforestation in Queensland’s forested bioregions. I then combined these models with vegetation community mapping in Queensland and 3 calculated which communities were likely to migrate into a higher vulnerability status (ie a least concern community becoming endangered). Using scenarios which constituted the projected severity of land-clearing, I identified between 29 and 212 communities are likely to increase in their vulnerability status. Of these, between five and 20 communities are likely to go extinct if no action is taken. To prevent such loss, it is imperative that policy intervention target areas with high vulnerability to future loss. Recommendations for these targeting areas with a high vulnerability to future loss are provided in the final chapter (Chapter 6). I build on the information developed in the first five chapters of this work to provide recommendations which link conservation outcomes to biodiversity threats and the types of decisions required of governments to maximise impact. To ensure that these recommendations are practical and feasible, I have worked closely with decision-makers throughout this project. This collaboration ensures the policy relevance of the work useful while also maintaining robust scientific methods. By achieving the objectives listed above, my thesis provides an essential contribution to future protected area policy and the academic literature concerning conservation planning by assessing current forests retention mechanisms and providing strong recommendations for policy.
View
... Thinning is one of the main strategies of forest management (Houghton, 2005;Peres et al., 2006). Reducing stand density and regulating stand structure by removing individual trees from a stand improves forest vegetation community diversity and enhances forest ecosystem stability (Reich, 2011;Li et al., 2020). Thinning alters the carbon sequestration capacity by affecting the forest microclimate and soil physicochemical properties (Hoen and Solberg, 1994;Ma et al., 2022b). ...
Thinning increases forest ecosystem carbon stocks
Article
  • Mar 2024
  • FOREST ECOL MANAG
Thinning, a major measure of forest management, is known to alter carbon sequestration by affecting the forest microclimate and soil environmental conditions. However, how thinning effect on forest ecosystem carbon stocks have presented inconsistent results. Therefore, we conducted 1776 pairs of thinning experiment observations worldwide to explore how thinning affects forest vegetation and soil carbon stocks. The results showed that overall thinning significantly increased total tree aboveground biomass carbon stocks (AGC total , +23.9%, +1.3 Mg ha-1 yr-1), understory vegetation carbon stocks (UVC, +68.3%, 0.12 Mg ha-1 yr-1), and soil organic carbon stocks (SOC stocks , +4.8%, 1.0 Mg ha-1 yr-1) at the global, but exhibited significantly decreased carbon stocks of litterfall (LBC,-9.6%,-0.03 Mg ha-1 yr-1). Belowground biomass carbon stocks remained unchanged under thinning. The sensitivity of carbon sequestration to thinning gradually disappeared after 6 years, except for AGC total , as they were jointly subject to stand density and thinning intensity and not just recovery ages. The response to UVC was more positive in medium-density (1500-3000 trees ha-1) and moderately thinned (30-50%) stands, and the thinning effects on UVC and SOC stocks were more noticeable in the subtropical and temperate zones. In summary, thinning enhanced forest ecosystem carbon sinks (+2.4 Mg ha-1 yr-1) but reduced carbon stocks in low-density stands (≤ 1500 trees ha-1). Soil moisture content (SMC, +6.6%) and bulk density (BD,-1.5%) dynamics after thinning were important factors regulating vegetation growth and soil carbon cycling processes.
View
... At the same time, the need to rapidly decrease net carbon emissions in order to reduce the risk of catastrophic climate change has given renewed importance to forests and their management. Forests have a key role to play in future carbon cycling (Reich, 2011), as they have the potential to take up and store large quantities of carbon, although that potential depends crucially on how forests are managed. ...
View
... Forest is an important part of terrestrial ecosystems and plays a significant role in soil and water conservation, atmospheric carbon dioxide (CO 2 ) absorption, and mitigating global warming. 1,2 Forests show different phenological characteristics in the structure and function in different seasons at landscape scale. 3 The forest phenology has been a hot issue in the field of global change research. ...
View
... forests-and-climate-change). Although forests behave as carbon sources due to land-use changes and deforestation by anthropogenic or natural disturbances (Pan et al., 2011;Reich, 2011), they can also act as carbon sinks through significant reforestation and sustainable forest management practices (Brown et al., 1996;Folland et al., 2001). ...
Spatiotemporal patterns and driving factors of carbon dynamics in forest ecosystems: A case study from Turkey
Article
  • May 2021
Evaluating the spatiotemporal patterns of carbon dynamics is critical for both understanding the role of forest ecosystems in the carbon cycle and developing effective forest policies to mitigate the impacts of climate change. This study analyzes the effects of spatiotemporal changes on carbon dynamics based on landscape structure for the Hisar Planning Unit, Turkey, using forest inventory data between 1973 and 2015. The total carbon stock increased from 1434.49 Gg in 1973 to 1919.37 Gg in 2015, an increase of 33.8%. The mean annual carbon storage was 11.54 Gg · year−1, including 4.28 Gg · year−1 in biomass and 7.26 Gg · year−1 in soil over four decades. The most significant carbon pool in the total carbon stock was from the soil, with 71.6%, 70.7%, and 69.4% of the total carbon storage in 1973, 1998, and 2015, respectively. Pure pine stands, overmature development stages, fully covered stands, and older forests were the prevailing factors affecting carbon density. The conversion from degraded (1442.47 ha, 14.85%), coppice (157.04 ha, 3.9%), and non-forest lands (1412.91 ha, 5.2%) to productive forests with afforestation or restoration activities significantly boosted the total carbon storage. Furthermore, increasing awareness and stewardship in forest management coupled with improved economic well-being reduced the pressure on the forests, leading to an increase in the quality of forest structure. These changes in landscape structure resulted in the heterogeneous distribution of carbon dynamics. In conclusion, understanding the spatiotemporal patterns of carbon dynamics is crucial for both forest managers and policy-makers in developing sustainable forest management practices and climate mitigation strategies for ecological sustainability and climate-smart forestry. Integr Environ Assess Manag 2022;18:209–223. © 2021 SETAC KEY POINTS Land use and land cover changes largely affect C storage and its spatial distribution. Improvement of forest structure for C storage is critical in mitigating climate change. The spatial distribution of C is a vital decision-support tool for foresters in the development of sound and practical strategies for afforestation and rehabilitation. It was clear that depopulation in rural areas, decrease in forest crime, and increase in local income levels are essential indicators of rural developments including social awareness and sensitivity to the environment.
View
... The vegetation gains carbon from productivity investment in plant growth and loses carbon through aging, mortality, harvest, etc. (Myneni et al., 2001). Although tropical forests have high carbon storage capacity (Pan et al., 2011;Reich, 2011), they are threatened by anthropogenic activities such as deforestation, farming and urbanization. However, major knowledge gaps in tropical forest dynamics and ecology exist. ...
View
... The vegetation gains carbon from productivity investment in plant growth and loses carbon through aging, mortality, harvest, etc. (Myneni et al., 2001). Although tropical forests have high carbon storage capacity (Pan et al., 2011;Reich, 2011), they are threatened by anthropogenic activities such as deforestation, farming and urbanization. However, major knowledge gaps in tropical forest dynamics and ecology exist. ...
TREE DIVERSITY PATTERNS, ABOVE-GROUND BIOMASS AND CARBON ASSESSMENT ALONG ELEVATIONAL GRADIENT IN A TROPICAL FOREST OF THE CAMEROON VOLCANIC LINE
Article
Full-text available
  • Jul 2020
Tropical forests ecosystems remain the most diverse on the planet, and store considerable amounts of biomass and carbon. Despite the importance of tropical forests, sizable knowledge gaps exist regarding species diversity, plant biomass and carbon. These knowledge gaps are particularly large in tropical systems, and even more so in the African tropics. This study provides baseline data on species composition and vegetation structure, and evaluate variation along elevational gradient transecting of four elevation-forest types: lowland, mid-elevation, sub-montane and montane forest in the Rumpi Hills Forest Reserve of Cameroon. We collected data on tree species diversity, above-ground biomass and carbon in 25 1-ha plots sampled in 500 m long x 20 m width transect. Results revealed high species diversity, particularly in lowland forest. Overall, the study enumerated 12,037 individuals (trees ≥ 10 cm dbh) of 441 species. The mean species per plot decreased with increasing elevation, 112 in lowland, 81 in mid-elevation, 60 in submontane and 38 in montane forest. Above-ground carbon averaged 162.88±50 t ha-1. We found the greatest carbon storage and tree and liana species diversity at low elevations. Our results indicate that high species diversity and occurrence of larger tree species are more important in carbon storage in lowland forest than at higher elevations. These findings are useful for management and land use planning of the forests in the Rumpi Hills Forest Reserve.
View
Contribution of vegetation restoration to carbon sequestration driven by ex‐situ poverty alleviation and relocation in ecologically fragile areas—Taking Guizhou, China, as a case
Article
  • May 2023
Vegetation restoration in ecologically fragile areas has a significant carbon sequestration (CS) effect. However, it is usually difficult to achieve quantitative assessment at the regional scale for this part of human activity intervention. The Chinese government's ex‐situ poverty alleviation and relocation (EPAR) project has relocated approximately 10 million people from areas with a fragile ecological environment to urban centralized resettlement, which is a typical case of weakened environmental intervention by human activities (Guizhou Province accounting for approximately 20% of the total relocated population in China). The CS model of vegetation photosynthesis and spatial analysis of geographic information were used to quantify the contribution of human activities to the natural restoration of vegetation CS, based on the data of net primary productivity (NPP) of vegetation from 2000 to 2020. The results show that the implementation of the EPAR project acts as an external force to drive vegetation restoration and CS, which increases the slope of the carbon density change trend (from k = 30.9 to k = 57.41), resulting in an overall carbon density increase of 26.51 tCkm ⁻² . The regional spatial analysis showed that the correlation coefficients between carbon density and relocation intensity in the 5‐year and 10‐year change were r = 0.976 ( p < 0.01) and r = 0.949 ( p < 0.05), respectively, indicating a significant positive correlation. Based on this, the CS contribution of vegetation in 84 districts in Guizhou Province that implemented EPAR projects was calculated, showing that 79 districts contributed positively, accounting for 94%. The average contribution of CS by vegetation restoration in each district was 0.0556 Tg, and offset CO 2 emissions were 0.2059 Tg. The other five districts with a negative contribution to CS were distributed in regions with relatively stable ecosystems and mature forests. This shows that human intervention in the environment changes more significantly in fragile ecological areas.
View
China's carbon budget inventory from 1997 to 2017 and its challenges to achieving carbon neutral strategies
Article
  • Mar 2022
  • J CLEAN PROD
The global climate change situation partly depends on the climate change policies of countries around the world, including China. Therefore, it is necessary to reasonably reduce carbon emissions (CEs) and increase carbon sink in order to progressively achieve the carbon neutral (CN) goal. However, the capacity and the potential to achieve carbon neutral with the support of its ecosystem, that is to say the carbon neutral capacity (CNC) and potential, are still unclear. To this end, based on China's energy emissions data, meteorological and hydrological data, lithology data, and vegetation data, we used the GEM-CO2 model, soil respiration model, spatial autocorrelation analysis method and other methods to establish the spatial information map of China city-scale CNC from 1997 to 2017. Furthermore, based on the future climate, vegetation data, CEs data and their influencing factors in 2025–2060, the Back Propagation neural network model was used to predict the CN potential of China's provinces. This study found during the study period, annual CEs of 5.63 Pg CO2 were not absorbed, which is about 90% of the average annual CEs. And the carbon surplus regions were mainly concentrated in the less developed northeastern and southwestern border regions. Moreover, the change in the CNC in China from 1997 to 2017 was −13.37 Tg/yr, indicating that the CNC of China's terrestrial ecosystems overall reduced. It should be noted that most provinces are not highly polarized, that is, there is no significant differences in CNC between cities in the provinces. Moreover, the scenario simulation's method of IPCC provides a reference for this manuscript, so we set up two future scenarios (A2 and B1 scenarios). In the future, China is expected to achieve a carbon emission peak before 2030 under the B1 scenario while it will continue to grow under the A2 scenario. From 2017 to 2060, the CNC under the two scenarios (A2/B1) will decrease by 44.58% and increase by 15.54%. It follows then that the road to CN in China will be difficult without corresponding policy intervention. In short, this study has clarified China's CNC from the past to the future, as well as CNC's spatial distribution and changing trends. This provided theoretical and data support for China to introduce corresponding zero-carbon solutions based on its understanding of CNC.
View
The impact of strictly protected areas in a deforestation hotspot
Article
Full-text available
  • Jul 2021
Protected areas are often thought of as a key conservation strategy for avoiding deforestation and retaining biodiversity; therefore, it is crucial to know how effective they are at achieving this purpose. Using a case study from Queensland, Australia, we identified and controlled for bias in allocating strictly protected areas (IUCN Class I and II) and evaluated their impact (in terms of avoiding deforestation) using statistical matching methods. Over the 30 years between 1988 and 2018, approximately 70,481 km2 of native forest was cleared in the study region. Using statistical matching, we estimated that 10.5% (1,447 km2) of Category I and II (strict) protected areas would have been cleared in the absence of protection. Put differently, 89.5% of strictly protected areas are unlikely to have been cleared, even if they were never protected. While previous studies have used statistical matching at a country or state level, we conducted an analysis that allows regional comparison across a single State. Our research indicates that strictly protected areas are marginally effective at preventing deforestation, and this likely due to biases in establishing protected areas on unproductive land.
View
Trends in the sources and sinks of carbon dioxide
Article
Full-text available
  • Nov 2009
Efforts to control climate change require the stabilization of atmospheric CO2 concentrations. This can only be achieved through a drastic reduction of global CO2 emissions. Yet fossil fuel emissions increased by 29% between 2000 and 2008, in conjunction with increased contributions from emerging economies, from the production and international trade of goods and services, and from the use of coal as a fuel source. In contrast, emissions from land-use changes were nearly constant. Between 1959 and 2008, 43% of each year's CO2 emissions remained in the atmosphere on average; the rest was absorbed by carbon sinks on land and in the oceans. In the past 50 years, the fraction of CO2 emissions that remains in the atmosphere each year has likely increased, from about 40% to 45%, and models suggest that this trend was caused by a decrease in the uptake of CO2 by the carbon sinks in response to climate change and variability. Changes in the CO2 sinks are highly uncertain, but they could have a significant influence on future atmospheric CO2 levels. It is therefore crucial to reduce the uncertainties.
View
A Large and Persistent Carbon Sink in the World's Forests
Article
Full-text available
  • Aug 2011
  • SCIENCE
The terrestrial carbon sink has been large in recent decades, but its size and location remain uncertain. Using forest inventory data and long-term ecosystem carbon studies, we estimate a total forest sink of 2.4 ± 0.4 petagrams of carbon per year (Pg C year–1) globally for 1990 to 2007. We also estimate a source of 1.3 ± 0.7 Pg C year–1 from tropical land-use change, consisting of a gross tropical deforestation emission of 2.9 ± 0.5 Pg C year–1 partially compensated by a carbon sink in tropical forest regrowth of 1.6 ± 0.5 Pg C year–1. Together, the fluxes comprise a net global forest sink of 1.1 ± 0.8 Pg C year–1, with tropical estimates having the largest uncertainties. Our total forest sink estimate is equivalent in magnitude to the terrestrial sink deduced from fossil fuel emissions and land-use change sources minus ocean and atmospheric sinks.
View
Increased soil emissions of potent greenhouse gases under increased atmospheric CO2
Article
Full-text available
  • Jul 2011
  • NATURE
Increasing concentrations of atmospheric carbon dioxide (CO(2)) can affect biotic and abiotic conditions in soil, such as microbial activity and water content. In turn, these changes might be expected to alter the production and consumption of the important greenhouse gases nitrous oxide (N(2)O) and methane (CH(4)) (refs 2, 3). However, studies on fluxes of N(2)O and CH(4) from soil under increased atmospheric CO(2) have not been quantitatively synthesized. Here we show, using meta-analysis, that increased CO(2) (ranging from 463 to 780 parts per million by volume) stimulates both N(2)O emissions from upland soils and CH(4) emissions from rice paddies and natural wetlands. Because enhanced greenhouse-gas emissions add to the radiative forcing of terrestrial ecosystems, these emissions are expected to negate at least 16.6 per cent of the climate change mitigation potential previously predicted from an increase in the terrestrial carbon sink under increased atmospheric CO(2) concentrations. Our results therefore suggest that the capacity of land ecosystems to slow climate warming has been overestimated.
View
Inverse modeling of CO2 sources and sinks using satellite observations of CO2 from TES and surface flask measurements
Article
Full-text available
We infer CO2 surface fluxes using satellite observations of mid-tropospheric CO2 from the Tropospheric Emission Spectrometer (TES) and measurements of CO2 from surface flasks in a time-independent inversion analysis based on the GEOS-Chem model. Using TES CO2 observations over oceans, spanning 40° S–40° N, we find that the horizontal and vertical coverage of the TES and flask data are complementary. This complementarity is demonstrated by combining the datasets in a joint inversion, which provides better constraints than from either dataset alone, when a posteriori CO2 distributions are evaluated against independent ship and aircraft CO2 data. In particular, the joint inversion offers improved constraints in the tropics where surface measurements are sparse, such as the tropical forests of South America, which the joint inversion suggests was a weak sink of −0.17 ± 0.20 Pg C in 2006. Aggregating the annual surface-to-atmosphere fluxes from the joint inversion yields −1.13 ± 0.21 Pg C for the global ocean, −2.77 ± 0.20 Pg C for the global land biosphere and −3.90 ± 0.29 Pg C for the total global natural flux (defined as the sum of all biospheric, oceanic, and biomass burning contributions but excluding CO2 emissions from fossil fuel combustion). These global ocean, global land and total global fluxes are shown to be in the range of other inversion results for 2006. To achieve these results, a latitude dependent bias in TES CO2 in the Southern Hemisphere was assessed and corrected using aircraft flask data, and we demonstrate that our results have low sensitivity to variations in the bias correction approach. Overall, this analysis suggests that future carbon data assimilation systems can benefit by integrating in situ and satellite observations of CO2 and that the vertical information provided by satellite observations of mid-tropospheric CO2 combined with measurements of surface CO2, provides an important additional constraint for flux inversions.
View
Changing Ecology of Tropical Forests: Evidence and Drivers
Article
Full-text available
  • Feb 2009
Global environmental changes may be altering the ecology of tropical forests. Long-term monitoring plots have provided much of the evidence for large-scale, directional changes in tropical forests, but the results have been controversial. Here we review evidence from six complementary approaches to understanding possible changes: plant physiology experiments, long-term monitoring plots, ecosystem flux techniques, atmospheric measurements, Earth observations, and global-scale vegetation models. Evidence from four of these approaches suggests that large-scale, directional changes are occurring in the ecology of tropical forests, with the other two approaches providing inconclusive results. Collectively, the evidence indicates that both gross and net primary productivity has likely increased over recent decades, as have tree growth, recruitment, and mortality rates, and forest biomass. These results suggest a profound reorganization of tropical forest ecosystems. We evaluate the most likely drivers of the suite of changes, and suggest increasing resource availability, potentially from rising atmospheric CO2 concentrations, is the most likely cause.
View
Canopy nitrogen, carbon assimilation, and albedo in temperate and boreal forests: Functional relations and potential climate feedbacks
Article
Full-text available
  • Jan 2009
  • P NATL ACAD SCI USA
The availability of nitrogen represents a key constraint on carbon cycling in terrestrial ecosystems, and it is largely in this capacity that the role of N in the Earth's climate system has been considered. Despite this, few studies have included continuous variation in plant N status as a driver of broad-scale carbon cycle analyses. This is partly because of uncertainties in how leaf-level physiological relationships scale to whole ecosystems and because methods for regional to continental detection of plant N concentrations have yet to be developed. Here, we show that ecosystem CO(2) uptake capacity in temperate and boreal forests scales directly with whole-canopy N concentrations, mirroring a leaf-level trend that has been observed for woody plants worldwide. We further show that both CO(2) uptake capacity and canopy N concentration are strongly and positively correlated with shortwave surface albedo. These results suggest that N plays an additional, and overlooked, role in the climate system via its influence on vegetation reflectivity and shortwave surface energy exchange. We also demonstrate that much of the spatial variation in canopy N can be detected by using broad-band satellite sensors, offering a means through which these findings can be applied toward improved application of coupled carbon cycle-climate models.
View
Risk of natural disturbance makes future contribution of Canada's forests to the global carbon cycle highly uncertain
Article
Full-text available
  • Mar 2008
  • P NATL ACAD SCI USA
A large carbon sink in northern land surfaces inferred from global carbon cycle inversion models led to concerns during Kyoto Protocol negotiations that countries might be able to avoid efforts to reduce fossil fuel emissions by claiming large sinks in their managed forests. The greenhouse gas balance of Canada's managed forest is strongly affected by naturally occurring fire with high interannual variability in the area burned and by cyclical insect outbreaks. Taking these stochastic future disturbances into account, we used the Carbon Budget Model of the Canadian Forest Sector (CBM-CFS3) to project that the managed forests of Canada could be a source of between 30 and 245 Mt CO2e yr⁻¹ during the first Kyoto Protocol commitment period (2008–2012). The recent transition from sink to source is the result of large insect outbreaks. The wide range in the predicted greenhouse gas balance (215 Mt CO2e yr⁻¹) is equivalent to nearly 30% of Canada's emissions in 2005. The increasing impact of natural disturbances, the two major insect outbreaks, and the Kyoto Protocol accounting rules all contributed to Canada's decision not to elect forest management. In Canada, future efforts to influence the carbon balance through forest management could be overwhelmed by natural disturbances. Similar circumstances may arise elsewhere if global change increases natural disturbance rates. Future climate mitigation agreements that do not account for and protect against the impacts of natural disturbances, for example, by accounting for forest management benefits relative to baselines, will fail to encourage changes in forest management aimed at mitigating climate change. • greenhouse gases • factoring out • mitigation options • forest management • Kyoto Protocol
View
Drought-Induced Reduction in Global Terrestrial Net Primary Production from 2000 Through 2009
Article
  • Aug 2010
  • SCIENCE
Terrestrial net primary production (NPP) quantifies the amount of atmospheric carbon fixed by plants and accumulated as biomass. Previous studies have shown that climate constraints were relaxing with increasing temperature and solar radiation, allowing an upward trend in NPP from 1982 through 1999. The past decade (2000 to 2009) has been the warmest since instrumental measurements began, which could imply continued increases in NPP; however, our estimates suggest a reduction in the global NPP of 0.55 petagrams of carbon. Large-scale droughts have reduced regional NPP, and a drying trend in the Southern Hemisphere has decreased NPP in that area, counteracting the increased NPP over the Northern Hemisphere. A continued decline in NPP would not only weaken the terrestrial carbon sink, but it would also intensify future competition between food demand and proposed biofuel production.
View
Offset of the potential carbon sink from boreal forestation by decreases in surface Albedo
Article
  • Dec 2000
Carbon uptake by forestation is one method proposed to reduce net carbon dioxide emissions to the atmosphere and so limit the radiative forcing of climate change. But the overall impact of forestation on climate will also depend on other effects associated with the creation of new forests. In particular, the albedo of a forested landscape is generally lower than that of cultivated land, especially when snow is lying, and decreasing albedo exerts a positive radiative forcing on climate. Here I simulate the radiative forcings associated with changes in surface albedo as a result of forestation in temperate and boreal forest areas, and translate these forcings into equivalent changes in local carbon stock for comparison with estimated carbon sequestration potentials. I suggest that in many boreal forest areas, the positive forcing induced by decreases in albedo can offset the negative forcing that is expected from carbon sequestration. Some high-latitude forestation activities may therefore increase climate change, rather than mitigating it as intended.
View
  • Jan 2006
  • 611-636
  • P B Reich
  • B A Hungate
  • Y Luo
Reich, P. B., Hungate, B. A. & Luo, Y. Annu. Rev. Ecol. Syst. 37, 611-636 (2006).