Global Reforestation Research Articles

Deforestation as an Anthropogenic Driver of Mercury Pollution.

Deforestation reduces the capacity of the terrestrial biosphere to take up toxic pollutant mercury (Hg) and enhances the release of secondary Hg from soils. The consequences of deforestation for Hg cycling are not currently considered by anthropogenic emission inventories or specifically addressed under the global Minamata Convention on Mercury. Using global Hg modeling constrained by field observations, we estimate that net Hg fluxes to the atmosphere due to deforestation are 217 Mg year-1 (95% confidence interval (CI): 134-1650 Mg year-1) for 2015, approximately 10% of global primary anthropogenic emissions. If deforestation of the Amazon rainforest continues at business-as-usual rates, net Hg emissions from the region will increase by 153 Mg year-1 by 2050 (CI: 97-418 Mg year-1), enhancing the transport and subsequent deposition of Hg to aquatic ecosystems. Substantial Hg emissions reductions are found for two potential cases of land use policies: conservation of the Amazon rainforest (92 Mg year-1, 95% CI: 59-234 Mg year-1) and global reforestation (98 Mg year-1, 95% CI: 64-449 Mg year-1). We conclude that deforestation-related emissions should be incorporated as an anthropogenic source in Hg inventories and that land use policy could be leveraged to address global Hg pollution.

Impacts of pastures and forestry plantations on herpetofauna: A global meta‐analysis

Abstract The establishment of pastures and forestry plantations has increased globally to meet growing demands for meat and wood products. Pasture and plantation expansion often drives deforestation, which causes homogenization of biotic communities and is a major driver of the global extinction crisis. A core question is how the severity of losses varies between pastures and plantations, and in turn, how geographical location and plantation management characteristics moderate these impacts. Focusing on herpetofauna (amphibians and reptiles) as the most endangered vertebrate group, we performed a global synthesis using 41 scientific articles that reported species richness or abundance in pastures and forestry plantations relative to natural forest in 191 case studies among 19 countries. We found a severe negative effect of pasture and a less negative effect of forestry plantations on species richness and abundance of herpetofauna. Within plantations, species richness and total abundance were more negatively impacted in amphibians than reptiles, in the tropics, when planting exotic tree species, monocultures, large or commercial plantations, and when clearing understory vegetation. Yet mixed, old, small or conservation plantations and those permitting recovery of understory vegetation had no negative impacts relative to the reference natural forest. Synthesis and applications. The loss of herpetofauna species richness and abundance underscores the importance of halting ongoing tropical deforestation for pasture and intensive forestry plantations. The potential for appropriately managed forestry plantations to support biodiversity in regions lacking forest cover, including via replacement of anthropogenic pastures, suggests that such plantations have an important role under global reforestation agendas.

Large-scale reforestation can increase water yield and reduce drought risk for water-insecure regions in the Asia-Pacific.

Large-scale reforestation can potentially bring both benefits and risks to the water cycle, which needs to be better quantified under future climates to inform reforestation decisions. We identified 477 water-insecure basins worldwide accounting for 44.6% (380.2Mha) of the global reforestation potential. As many of these basins are in the Asia-Pacific, we used regional coupled land-climate modeling for the period 2041-2070 to reveal that reforestation increases evapotranspiration and precipitation for most water-insecure regions over the Asia-Pacific. This resulted in a statistically significant increase in water yield (p<.05) for the Loess Plateau-North China Plain, Yangtze Plain, Southeast China, and Irrawaddy regions. Precipitation feedback was influenced by the degree of initial moisture limitation affecting soil moisture response and thus evapotranspiration, as well as precipitation advection from other reforested regions and moisture transport away from the local region. Reforestation also reduces the probability of extremely dry months in most of the water-insecure regions. However, some regions experience nonsignificant declines in net water yield due to heightened evapotranspiration outstripping increases in precipitation, or declines in soil moisture and advected precipitation.

ReforesTree: A Dataset for Estimating Tropical Forest Carbon Stock with Deep Learning and Aerial Imagery

Forest biomass is a key influence for future climate, and the world urgently needs highly scalable financing schemes, such as carbon offsetting certifications, to protect and restore forests. Current manual forest carbon stock inventory methods of measuring single trees by hand are time, labour, and cost intensive and have been shown to be subjective. They can lead to substantial overestimation of the carbon stock and ultimately distrust in forest financing. The potential for impact and scale of leveraging advancements in machine learning and remote sensing technologies is promising, but needs to be of high quality in order to replace the current forest stock protocols for certifications. In this paper, we present ReforesTree, a benchmark dataset of forest carbon stock in six agro-forestry carbon offsetting sites in Ecuador. Furthermore, we show that a deep learning-based end-to-end model using individual tree detection from low cost RGB-only drone imagery is accurately estimating forest carbon stock within official carbon offsetting certification standards. Additionally, our baseline CNN model outperforms state-of-the-art satellite-based forest biomass and carbon stock estimates for this type of small-scale, tropical agro-forestry sites. We present this dataset to encourage machine learning research in this area to increase accountability and transparency of monitoring, verification and reporting (MVR) in carbon offsetting projects, as well as scaling global reforestation financing through accurate remote sensing.

Monitoring vegetation dynamics with open earth observation tools: the case of fire-modulated savanna to forest transitions in Central Africa

Woody encroachment and forest progression are widespread in forest-savanna transitional areas in Central Africa. Quantifying these dynamics and understanding their drivers at relevant spatial scales has long been a challenge. Recent progress in open access imagery sources with improved spatial, spectral and temporal resolution combined with cloud computing resources, and the advent of relatively cheap solutions to deploy laser sensors in the field, have transformed this domain of study. We present a study case in the Mpem & Djim National Park (MDNP), a 1,000 km2 protected area in the Centre region of Cameroon. Using open source algorithms in Google Earth Engine (GEE), we characterized vegetation dynamics and the fire regime based on Landsat multispectral imagery archive (1975–2020). Current species assemblages were estimated from Sentinel 2 imagery and the open source biodivMapR package, using spectral dissimilarity. Vegetation structure (aboveground biomass; AGB) was characterized using Unmanned Aerial vehicle (UAV) LiDAR scanning data sampled over the study area. Savanna vegetation, which was initially dominant in the MDNP, lost about 50% of its initial cover in <50 years in favor of forest at an average rate of ca. 0.63%.year−1 (6 km2.year−1). Species assemblage computed from spectral dissimilarity in forest vegetation followed a successional gradient consistent with forest age. AGB accumulation rate was 3.2 Mg.ha−1.year−1 after 42 years of forest encroachment. In savannas, two modes could be identified along the gradient of spectral species assemblage, corresponding to distinct AGB levels, where woody savannas with low fire frequency store 40% more AGB than open grassy savannas with high fire frequency. A fire occurrence every five year was found to be the fire regime threshold below which woody savannas start to dominate over grassy ones. A fire frequency below that threshold opens the way to young forest transitions. These results have implications for carbon sequestration and biodiversity conservation policies. Maintaining savanna ecosystems in the region would require active management actions to limit woody encroachment and forest progression, in contradiction with global reforestation goals.

Symphony for the native wood(s): Global reforestation as an opportunity to develop a culture of conservation

AbstractThe stewardship of forests across multiple human generations has potential to lead to cultural innovations fostering sustainable uses. Nevertheless, positive culture–nature interactions are often disrupted due to colonial exploitation and a lack of intrinsic value ascribed to nature in capitalist economies. There is global recognition that restoring degraded ecosystems is critical to promote the welfare of people and nature by reducing the negative impacts of global climate change and diminishing biodiversity. However, with a focus on technical remedies, restoration and reforestation efforts generally fail to address the root causes of ecosystem degradation.In this perspective paper, we call for explicit incorporation of cultural values into global reforestation efforts. We focus on music as a cultural ecosystem service as music has been a prominent part of human history with clear sociological and psychological attributes that may invite mass interest and participation. We illustrate the value of musical linkages via three case studies from Europe, Africa and Hawaii focusing on native tree species, their wood, musical ecology and their interaction with culture.We show that multi‐generational stewardship of native ecosystems in Europe has allowed the refinement of the violin to its current form, one that is culturally significant for millions of people and has created a multi‐million dollar industry. This development stems from a 500‐year tradition of craftsmanship handed down across generations and illustrates that ecocultural interactions can be a strong dynamo for development of unique commodities.In contrast, in regions where extirpation of native plant species was used as a deliberate colonization strategy, many ecocultural linkages face risk of extinction. Our case studies from Africa and Hawaii illustrate how native tree species of particular value for musical expression were nearly lost and along with loss of music, important cultural connections to nature.In the context of restoration, there is also evidence that music‐based linkages can revitalize nature–culture interactions and promote restoration of native ecosystems. Incorporating native trees in global reforestation efforts is critical for ensuring that reforestation efforts capture the synergies needed for developing new ideologies that promote the well‐being of co‐dependent humans and all life.

Diverse forests are cool: Promoting diverse forests to mitigate carbon emissions and climate change

AbstractClimate change is one of the most pressing threats to humanity, inducing a global increase in temperatures and more frequent extreme climatic events. Considering this, global reforestation initiatives are proposed to capture carbon and mitigate climate change. Global restoration and reforestation programs and their targets have inspired both unparalleled enthusiasm worldwide and intense scientific criticism and debate regarding their feasibility and implementation. We agree that global reforestation forecasting and efforts require a nuanced discussion and approach. In that vein, we would like to emphasize the potential of increasing existing forest diversity to enhance climate change mitigation by increasing aboveground and belowground carbon storage. Moreover, we argue that focusing on planting diverse forests in reforestation efforts can help to reduce climate change effects on ecosystems: first, by increasing resistance and resilience to extreme climatic events, and second, by buffering microclimatic conditions in natural and urban areas. Diversifying forests plantations and reforestation projects may not always be feasible and cannot solve the climate crisis by itself. However, we highlight that a focus on diverse forests could maximize the benefits of reforestation programs by promoting sustainable land management.

Challenges to the Reforestation Pipeline in the United States

Large-scale global reforestation goals have been proposed to help mitigate climate change and provide other ecosystem services. To explore reforestation potential in the United States, we used GIS analyses, surveys of nursery managers and foresters, and literature synthesis to assess the opportunities and challenges associated with meeting proposed reforestation goals. We considered a scenario where 26 million hectares (64 million acres) of natural and agricultural lands are reforested by 2040 with 30 billion trees at an estimated cost of $33 ($24–$53) billion USD. Cost per hectare will vary by region, site conditions, and other factors. This scenario would require increasing the number of tree seedlings produced each year by 1.7 billion, a 2.3-fold increase over current nursery production levels. Additional investment (not included in the reforestation cost estimate) will be needed to expand capacity for seed collection, seedling production, workforce development, and improvements in pre- and post-planting practices. Achieving this scenario will require public support for investing in these activities and incentives for landowners.

Global reforestation and biodiversity conservation.

The loss of forest is a leading cause of species extinction, and reforestation is 1 of 2 established interventions for reversing this loss. However, the role of reforestation for biodiversity conservation remains debated, and lacking is an assessment of the potential contribution that reforestation could make to biodiversity conservation globally. We conducted a spatial analysis of overlap between 1,550 forest-obligate threatened species' ranges and land that could be reforested after accounting for socioeconomic and ecological constraints. Reforestation on at least 43% (∼369 million ha) of reforestable area was predicted to potentially benefit threatened vertebrates. This is approximately 15% of the total area where threatened vertebrates occur. The greatest opportunities for conserving threatened vertebrate species are in the tropics, particularly Brazil and Indonesia. Although reforestation is not a substitute for forest conservation, and most of the area containing threatened vertebrates remains forested, our results highlight the need for global conservation strategies to recognize the potentially significant contribution that reforestation could make to biodiversity conservation. If implemented, reforestation of ∼369 million ha would also contribute substantially to climate-change mitigation, offering a way to achieve multiple sustainability commitments at once. Countries must now work to overcome key barriers (e.g., unclear revenue streams, high transaction costs) to investment in reforestation.

Rethinking global carbon storage potential of trees. A comment on Bastin et al. (2019)

Bastin et al. 2019 use two flawed assumptions: 1) that the area suitable for restoration does not contain any carbon currently, and 2) that soil organic carbon (SOC) from increased canopy cover will accumulate quickly enough to mitigate anthropogenic carbon emissions. We re-evaluated the potential carbon storage worldwide using empirical relationships of tree cover and carbon. We use global datasets of tree cover, soil organic carbon, and above ground biomass to estimate the empirical relationships of tree cover and carbon stock storage. A more realistic range of global carbon storage potential is between 71.7 and 75.7 GtC globally, with a large uncertainty associated with SOC. This is less than half of the original 205 GtC estimate. The potential global carbon storage of restored forests is much less than that estimated by Bastin et al. 2019. While we agree on the value of assessing global reforestation potential, we suggest caution in considering it the most effective strategy to mitigate anthropogenic emissions. A preprint version of this article was published on 13 August 2019 at https://doi.org/10.1101/730325

The impact of secondary forest regeneration on ground-dwelling ant communities in the Tropical Andes

Natural regeneration of abandoned farmland provides an important opportunity to contribute to global reforestation targets, including the Bonn Challenge. Of particular importance are the montane tropics, where a long history of farming, frequently on marginal soils, has rendered many ecosystems highly degraded and hotspots of extinction risk. Ants play crucial roles in ecosystem functioning, and a key question is how time since abandonment and elevation (and inherent temperature gradients therein) affect patterns of ant recovery within secondary forest systems. Focusing on the Colombian Andes across a 1300 m altitudinal gradient and secondary forest (2–30 years) recovering on abandoned cattle pastures, we find that over time ant community composition and species richness recovered towards that of primary forest. However, these relationships are strongly dependent on elevation with the more open and warmer pasturelands supporting more ants than either primary or secondary forest at a particular elevation. The loss of species richness and change in species composition with elevation is less severe in pasture than forests, suggesting that conditions within pasture and its remaining scattered trees, hedgerows and forest fragments, are more favourable for some species, which are likely in or near thermal debt. Promoting and protecting natural regenerating forests over the long term in the montane tropics will likely offer significant potential for returning ant communities towards primary forest levels.

Environmental benefits of modern power system and clean energy

Nowadays, the world is at a critical moment of facing serious environmental and economic problems. A very large number of people in developing countries is exposed to dangers associated with flammability and toxicity of traditional source of energy while others in industrialized countries are facing the effects of atmospheric air pollution and green house (GHG) gas emission .Despite the global reforestation policies, despite latest remarkable increase in renewable energy and natural gas production, there is still a problem of domination fuel and coal consumption. This paper explored the effects of rapid economic growth, industrial development on climate. Additionally the effects of continuous exponential population growth, a fast increase of energy global energy demand, conventional transport system on carbon and GHG emission have discussed. Finally the paper revealed how modern smart electricity system with sustainable energy system and electric transport system contribute to the reduction of hazardous emission.

Tree leaf trade-offs are stronger for sub-canopy trees: leaf traits reveal little about growth rates in canopy trees.

Can morphological plant functional traits predict demographic rates (e.g., growth) within plant communities as diverse as tropical forests? This is one of the most important next-step questions in trait-based ecology and particularly for global reforestation efforts. Due to the diversity of tropical tree species and their longevity, it is difficult to predict their performance prior to reforestation efforts. In this study, we investigate if simple leaf traits are predictors of the more complex ecological process of plant growth in regenerating selectively logged natural forest within the Wet Tropics (WTs) bioregion of Australia. This study used a rich historical data set to quantify tree growth within plots located at Danbulla National Park and State Forest on the Atherton Tableland. Leaf traits were collected from trees that have exhibited fast or slow growth over the last ~50yr of measurement. Leaf traits were found to be poor predictors of tree growth for trees that have entered the canopy; however, for sub-canopy trees, leaf traits had a stronger association with growth rates. Leaf phosphorus concentrations were the strongest predictor of Periodic Annual Increment (PAI) for trees growing within the sub-canopy, with trees with higher leaf phosphorus levels showing a higher PAI. Sub-canopy tree leaves also exhibited stronger trade-offs between leaf traits and adhere to theoretical predictions more so than for canopy trees. We suggest that, in order for leaf traits to be more applicable to reforestation, size dependence of traits and growth relationships need to be more carefully considered, particularly when reforestation practitioners assign mean trait values to tropical tree species from multiple canopy strata.

Global climate forcing from albedo change caused by large-scale deforestation and reforestation: quantification and attribution of geographic variation

Large-scale deforestation and reforestation have contributed substantially to historical and contemporary global climate change in part through albedo-induced radiative forcing, with meaningful implications for forest management aiming to mitigate climate change. Associated warming or cooling varies widely across the globe due to a range of factors including forest type, snow cover, and insolation, but resulting geographic variation remains poorly described and has been largely based on model assessments. This study provides an observation-based approach to quantify local and global radiative forcings from large-scale deforestation and reforestation and further examines mechanisms that result in the spatial heterogeneity of radiative forcing. We incorporate a new spatially and temporally explicit land cover-specific albedo product derived from Moderate Resolution Imaging Spectroradiometer with a historical land use data set (Land Use Harmonization product). Spatial variation in radiative forcing was attributed to four mechanisms, including the change in snow-covered albedo, change in snow-free albedo, snow cover fraction, and incoming solar radiation. We find an albedo-only radiative forcing (RF) of −0.819 W m−2 if year 2000 forests were completely deforested and converted to croplands. Albedo RF from global reforestation of present-day croplands to recover year 1700 forests is estimated to be 0.161 W m−2. Snow-cover fraction is identified as the primary factor in determining the spatial variation of radiative forcing in winter, while the magnitude of the change in snow-free albedo is the primary factor determining variations in summertime RF. Findings reinforce the notion that, for conifers at the snowier high latitudes, albedo RF diminishes the warming from forest loss and the cooling from forest gain more so than for other forest types, latitudes, and climate settings.

Forest transitions, trade, and the global displacement of land use

Reducing tropical deforestation is an international priority, given its impacts on carbon emissions and biodiversity. We examined whether recent forest transitions--a shift from net deforestation to net reforestation--involved a geographic displacement of forest clearing across countries through trade in agricultural and forest products. In most of the seven developing countries that recently experienced a forest transition, displacement of land use abroad accompanied local reforestation. Additional global land-use change embodied in their net wood trade offset 74% of their total reforested area. Because the reforesting countries continued to export more agricultural goods than they imported, this net displacement offset 22% of their total reforested area when both agriculture and forestry sectors are included. However, this net displacement increased to 52% during the last 5 y. These countries thus have contributed to a net global reforestation and/or decrease in the pressure on forests, but this global environmental benefit has been shrinking during recent years. The net decrease in the pressure on forests does not account for differences in their ecological quality. Assessments of the impacts of international policies aimed at reducing global deforestation should integrate international trade in agricultural and forest commodities.

Cost and performance of CO 2 storage in forestry projects

In order to include forestry projects in a possible CO 2 emission reduction regime, and to compare the costs of individual projects or national programs, it is necessary to determine the rate of equivalency between carbon in fossil fuel emissions and carbon stored in different types of forestry projects. This paper presents a comprehensive and consistent methodology to account for the costs and carbon flows of different categories of forestry projects and describes the application of the methodology to a set of projects in Central America. Several estimates have been made to date of the overall potential for carbon storage through global reforestation and the costs of such efforts, based on global macroeconomic estimates and extrapolations from current forest-sector experience. However, there has yet to be a consistent analysis of the magnitude and cost of carbon savings by a “bottom-up” approach to sustainable forestry development This methodology is applied to a set of projects proposed in Costa Rica and other Central American countries under the Tropical Forest Action Plan, to estimate a sample set of national CO 2 reduction cost curves. The costs of carbon savings in the forestry projects studied in Central America mostly fall between $5 and $13 ton-C 1, depending on the type of project, the climate, and the opportunity cost of land. These projects also promise socio-economic benefits at the local level, provided they are adequately endowed with funding, training and institutional support. The total amount of CO 2 storage potential is significant, about 100 million tons per country, but not enough to suggest that forestry can offset more than a few percent of global CO 2 emissions from fossil fuel use.