Quantifying the effectiveness of climate change mitigation through forest plantations and carbon sequestration with an integrated land-use model

Temperature overshoot responses to ambitious forestation in an Earth System Model

Despite the increasing relevance of temperature overshoot and the rather ambitious country pledges on Afforestation/Reforestation globally, the mitigation potential and the Earth system responses to large-scale non-idealized Afforestation/Reforestation patterns under a high overshoot scenario remain elusive. Here, we develop an ambitious Afforestation/Reforestation scenario by harnessing 1259 Integrated Assessment Model scenarios, restoration potential maps, and biodiversity constraints, reaching 595 Mha by 2060 and 935 Mha by 2100. We then force the Max Planck Institute's Earth System Model with this scenario which yields a reduction of peak temperature by 0.08 oC, end-of-century temperature by 0.2 oC, and overshoot duration by 13 years. Afforestation/Reforestation in the range of country pledges globally could thus constitute a useful mitigation tool in overshoot scenarios in addition to fossil fuel emission reductions, but socio-ecological implications need to be scrutinized to avoid severe side effects.

Empirical analysis of the feasible solution to mitigate the CO2 emission: evidence from Next-11 countries

From the empirical findings, economic growth, energy consumption, fossil fuel use, and infrastructure all have a positive impact on CO2 emissions. Forest rent and industrialization show a mix of results to explain CO2 emissions in N-11 countries. Forest and agriculture have negative coefficients in most of the estimations which indicate the reduction of CO2 emissions in 11 countries. Through the evidence of variance decomposition (VD) analysis, this study found an inverted U-shaped EKC hypothesis in the long run. Moreover, through the econometric analysis, it is clear that forest area is important to reduce CO2 emissions in N-11 countries, where forest investment and planning would be effective for carbon reduction. Agricultural activities and production with green investment play an important role in mitigating CO2 emissions in N-11 countries.

Survival, growth and carbon content in a forest plantation established after a clear-cutting in Durango, Mexico

Background

Forest plantations play an important role in carbon sequestration, helping to mitigate climate change. In this study, survival, biomass, growth rings and annual carbon content storage were evaluated in a mixed Pinus durangensis and P. cooperi plantation that was established after a clear-cutting. The plantation is eight years old and covers an area of 21.40 ha.

Methods

Sixteen sites of 100 m² were distributed randomly. At each site, two trees distributed proportionally to the diametric categories were destructively sampled (one per tree species). Two cross-sections were cut from each tree: The first at the base of the stump and the second at 1.30 m. The width of tree rings of the first cross-section was measured using a stereoscopic microscope with precision in microns (µm). The year-by-year basal diameter of each tree was recorded and biomass and carbon content was estimated using allometric equations.

Results

The estimated survival was 75.2%. The results of the ANOVA showed significant differences between the year-by-year width records of tree rings, the highest value corresponding to the fifth year. The average carbon sequestration per year is 0.30 kg for both studied tree species.

Conclusions

P. durangensis and P. cooperi plantations adapt and develop well in Durango forests when they are established in areas that are subjected to clear-cutting.

Early Detection of Invasive Exotic Trees Using UAV and Manned Aircraft Multispectral and LiDAR Data

Exotic conifers can provide significant ecosystem services, but in some environments, they have become invasive and threaten indigenous ecosystems. In New Zealand, this phenomenon is of considerable concern as the area occupied by invasive exotic trees is large and increasing rapidly. Remote sensing methods offer a potential means of identifying and monitoring land infested by these trees, enabling managers to efficiently allocate resources for their control. In this study, we sought to develop methods for remote detection of exotic invasive trees, namely Pinus sylvestris and P. ponderosa. Critically, the study aimed to detect these species prior to the onset of maturity and coning as this is important for preventing further spread. In the study environment in New Zealand’s South Island, these species reach maturity and begin bearing cones at a young age. As such, detection of these smaller individuals requires specialist methods and very high-resolution remote sensing data. We examined the efficacy of classifiers developed using two machine learning algorithms with multispectral and laser scanning data collected from two platforms—manned aircraft and unmanned aerial vehicles (UAV). The study focused on a localized conifer invasion originating from a multi-species pine shelter belt in a grassland environment. This environment provided a useful means of defining the detection thresholds of the methods and technologies employed. An extensive field dataset including over 17,000 trees (height range = 1 cm to 476 cm) was used as an independent validation dataset for the detection methods developed. We found that data from both platforms and using both logistic regression and random forests for classification provided highly accurate (kappa < 0.996 ) detection of invasive conifers. Our analysis showed that the data from both UAV and manned aircraft was useful for detecting trees down to 1 m in height and therefore shorter than 99.3% of the coning individuals in the study dataset. We also explored the relative contribution of both multispectral and airborne laser scanning (ALS) data in the detection of invasive trees through fitting classification models with different combinations of predictors and found that the most useful models included data from both sensors. However, the combination of ALS and multispectral data did not significantly improve classification accuracy. We believe that this was due to the simplistic vegetation and terrain structure in the study site that resulted in uncomplicated separability of invasive conifers from other vegetation. This study provides valuable new knowledge of the efficacy of detecting invasive conifers prior to the onset of coning using high-resolution data from UAV and manned aircraft. This will be an important tool in managing the spread of these important invasive plants.

Carbon dynamics on agricultural land reverting to woody land in Ontario, Canada

The 2015 Paris Agreement reinforces the importance of the land sector and its contribution to greenhouse gas (GHG) reductions. Thus, there is growing interest in improving estimates of the GHG balance in response to land-use changes (LUCs) involving agriculture and forestry, for national-scale reporting, and for carbon (C) offsets. Large agricultural areas in Europe, Russia and North America are reverting to forest, either naturally or through planting, after abandonment of agricultural land, and this trend may have a substantial impact on carbon budgets. We report results of a pilot project in the Mixedwood Plains ecozone of eastern Canada to analyze the change in the C budget on a landscape over 15 years on abandoned cropland where woody vegetation is regenerating. Thirty-six plots (2 km × 2 km) with paired aerial photographs taken circa 1994 and circa 2008 at a scale of 1:10,000 or larger were randomly selected from the 20 km × 20 km National Forest Inventory (NFI) grid. A spatially-explicit version of the Carbon Budget Model of the Canadian Forest Sector (CBM-CFS3) was used to estimate impacts of LUC on C stocks and fluxes. Polygons identifying areas of LUC within each photo plot were delineated, classified, and evaluated to provide input data for the model. The rate of C accumulation in our study area was found to be relatively constant over the entire simulation period, at 1.07 Mg C/ha/yr. Abandoned agricultural land reverting to woody lands could play an important role in regional and national C sequestration in Canada, but more research is required to quantify the areal extent of this LUC.

Climate change mitigation strategies in the forest sector: biophysical impacts and economic implications in British Columbia, Canada

Managing forests to increase carbon sequestration or reduce carbon emissions and using wood products and bioenergy to store carbon and substitute for other emission-intensive products and fossil fuel energy have been considered effective ways to tackle climate change in many countries and regions. The objective of this study is to examine the climate change mitigation potential of the forest sector by developing and assessing potential mitigation strategies and portfolios with various goals in British Columbia (BC), Canada. From a systems perspective, mitigation potentials of five individual strategies and their combinations were examined with regionally differentiated implementations of changes. We also calculated cost curves for the strategies and explored socio-economic impacts using an input-output model. Our results showed a wide range of mitigation potentials and that both the magnitude and the timing of mitigation varied across strategies. The greatest mitigation potential was achieved by improving the harvest utilization, shifting the commodity mix to longer-lived wood products, and using harvest residues for bioenergy. The highest cumulative mitigation of 421 MtCO₂e for BC was estimated when employing the strategy portfolio that maximized domestic mitigation during 2017-2050, and this would contribute 35% of BC's greenhouse gas emission reduction target by 2050 at less than $100/tCO₂e and provide additional socio-economic benefits. This case study demonstrated the application of an integrated systems approach that tracks carbon stock changes and emissions in forest ecosystems, harvested wood products (HWPs), and the avoidance of emissions through the use of HWPs and is therefore applicable to other countries and regions.

Global potential of biospheric carbon management for climate mitigation

Elevated concentrations of atmospheric greenhouse gases (GHGs), particularly carbon dioxide (CO2), have affected the global climate. Land-based biological carbon mitigation strategies are considered an important and viable pathway towards climate stabilization. However, to satisfy the growing demands for food, wood products, energy, climate mitigation and biodiversity conservation-all of which compete for increasingly limited quantities of biomass and land-the deployment of mitigation strategies must be driven by sustainable and integrated land management. If executed accordingly, through avoided emissions and carbon sequestration, biological carbon and bioenergy mitigation could save up to 38 billion tonnes of carbon and 3-8% of estimated energy consumption, respectively, by 2050.

Significant increase in ecosystem C can be achieved with sustainable forest management in subtropical plantation forests

Subtropical planted forests are rapidly expanding. They are traditionally managed for intensive, short-term goals that often lead to long-term yield decline and reduced carbon sequestration capacity. Here we show how it is possible to increase and sustain carbon stored in subtropical forest plantations if management is switched towards more sustainable forestry. We first conducted a literature review to explore possible management factors that contribute to the potentials in ecosystem C in tropical and subtropical plantations. We found that broadleaves plantations have significantly higher ecosystem C than conifer plantations. In addition, ecosystem C increases with plantation age, and reaches a peak with intermediate stand densities of 1500-2500 trees ha⁻¹. We then used the FORECAST model to simulate the regional implications of switching from traditional to sustainable management regimes, using Chinese fir (Cunninghamia lanceolata) plantations in subtropical China as a study case. We randomly simulated 200 traditional short-rotation pure stands and 200 sustainably-managed mixed Chinese fir--Phoebe bournei plantations, for 120 years. Our results showed that mixed, sustainably-managed plantations have on average 67.5% more ecosystem C than traditional pure conifer plantations. If all pure plantations were gradually transformed into mixed plantations during the next 10 years, carbon stocks could rise in 2050 by 260.22 TgC in east-central China. Assuming similar differences for temperate and boreal plantations, if sustainable forestry practices were applied to all new forest plantation types in China, stored carbon could increase by 1,482.80 TgC in 2050. Such an increase would be equivalent to a yearly sequestration rate of 40.08 TgC yr⁻¹, offsetting 1.9% of China's annual emissions in 2010. More importantly, this C increase can be sustained in the long term through the maintenance of higher amounts of soil organic carbon and the production of timber products with longer life spans.

Interactions between reducing CO2 emissions, CO2 removal and solar radiation management

We use a simple carbon cycle-climate model to investigate the interactions between a selection of idealized scenarios of mitigated carbon dioxide emissions, carbon dioxide removal (CDR) and solar radiation management (SRM). Two CO(2) emissions trajectories differ by a 15-year delay in the start of mitigation activity. SRM is modelled as a reduction in incoming solar radiation that fully compensates the radiative forcing due to changes in atmospheric CO(2) concentration. Two CDR scenarios remove 300 PgC by afforestation (added to vegetation and soil) or 1000 PgC by bioenergy with carbon capture and storage (removed from system). Our results show that delaying the start of mitigation activity could be very costly in terms of the CDR activity needed later to limit atmospheric CO(2) concentration (and corresponding global warming) to a given level. Avoiding a 15-year delay in the start of mitigation activity is more effective at reducing atmospheric CO(2) concentrations than all but the maximum type of CDR interventions. The effects of applying SRM and CDR together are additive, and this shows most clearly for atmospheric CO(2) concentration. SRM causes a significant reduction in atmospheric CO(2) concentration due to increased carbon storage by the terrestrial biosphere, especially soils. However, SRM has to be maintained for many centuries to avoid rapid increases in temperature and corresponding increases in atmospheric CO(2) concentration due to loss of carbon from the land.

Using land to mitigate climate change: hitting the target, recognizing the trade-offs

Land can be used in several ways to mitigate climate change, but especially under changing environmental conditions there may be implications for food prices. Using an integrated global system model, we explore the roles that these land-use options can play in a global mitigation strategy to stabilize Earth's average temperature within 2 °C of the preindustrial level and their impacts on agriculture. We show that an ambitious global Energy-Only climate policy that includes biofuels would likely not achieve the 2 °C target. A thought-experiment where the world ideally prices land carbon fluxes combined with biofuels (Energy+Land policy) gets the world much closer. Land could become a large net carbon sink of about 178 Pg C over the 21st century with price incentives in the Energy+Land scenario. With land carbon pricing but without biofuels (a No-Biofuel scenario) the carbon sink is nearly identical to the case with biofuels, but emissions from energy are somewhat higher, thereby results in more warming. Absent such incentives, land is either a much smaller net carbon sink (+37 Pg C - Energy-Only policy) or a net source (-21 Pg C - No-Policy). The significant trade-off with this integrated land-use approach is that prices for agricultural products rise substantially because of mitigation costs borne by the sector and higher land prices. Share of income spent on food for wealthier regions continues to fall, but for the poorest regions, higher food prices lead to a rising share of income spent on food.

Normative productivity of the global vegetation

BACKGROUND

The biosphere models of terrestrial productivity are essential for projecting climate change and assessing mitigation and adaptation options. Many of them have been developed in connection to the International Geosphere-Biosphere Program (IGBP) that backs the work of the Intergovernmental Panel on Climate Change (IPCC). In the end of 1990s, IGBP sponsored release of a data set summarizing the model outputs and setting certain norms for estimates of terrestrial productivity. Since a number of new models and new versions of old models were developed during the past decade, these normative data require updating.

RESULTS

Here, we provide the series of updates that reflects evolution of biosphere models and demonstrates evolutional stability of the global and regional estimates of terrestrial productivity. Most of them fit well the long-living Miami model. At the same time we call attention to the emerging alternative: the global potential for net primary production of biomass may be as high as 70 PgC y-1, the productivity of larch forest zone may be comparable to the productivity of taiga zone, and the productivity of rain-green forest zone may be comparable to the productivity of tropical rainforest zone.

CONCLUSION

The departure from Miami model's worldview mentioned above cannot be simply ignored. It requires thorough examination using modern observational tools and techniques for model-data fusion. Stability of normative knowledge is not its ultimate goal - the norms for estimates of terrestrial productivity must be evidence-based.

Carbon fluxes resulting from land-use changes in the Tamaulipan thornscrub of northeastern Mexico

Information on carbon stock and flux resulting from land-use changes in subtropical, semi-arid ecosystems are important to understand global carbon flux, yet little data is available. In the Tamaulipan thornscrub forests of northeastern Mexico, biomass components of standing vegetation were estimated from 56 quadrats (200 m2 each). Regional land-use changes and present forest cover, as well as estimates of soil organic carbon from chronosequences, were used to predict carbon stocks and fluxes in this ecosystem.For the period of 1980-1996, the Tamaulipan thornscrub is presenting an annual deforestation rate of 2.27% indicating that approximately 600 km2 of this plant community are lost every year and that 60% of the original Mexican Tamaulipan thornscrub vegetation has been lost since the 1950's. On the other hand, intensive agriculture, including introduced grasslands increased (4,000 km2) from 32 to 42% of the total studied area, largely at the expense of the Tamaulipan thornscrub forests. Land-use changes from Tamaulipan thornscrub forest to agriculture contribute 2.2 Tg to current annual carbon emissions and standing biomass averages 0.24 +/- 0.06 Tg, root biomass averages 0.17 +/- 0.03 Tg, and soil organic carbon averages 1.80 +/- 0.27 Tg. Land-use changes from 1950 to 2000 accounted for Carbon emissions of the order of 180.1 Tg. Projected land-use changes will likely contribute to an additional carbon flux of 98.0 Tg by the year 2100. Practices to conserve sequester, and transfer carbon stocks in semi-arid ecosystems are discussed as a means to reduce carbon flux from deforestation practices.