The restoration of trees remains among the most effective strategies for climate change mitigation. We mapped the global potential tree coverage to show that 4.4 billion hectares of canopy cover could exist under the current climate. Excluding existing trees and agricultural and urban areas, we found that there is room for an extra 0.9 billion hectares of canopy cover, which could store 205 gigatonnes of carbon in areas that would naturally support woodlands and forests. This highlights global tree restoration as our most effective climate change solution to date. However, climate change will alter this potential tree coverage. We estimate that if we cannot deviate from the current trajectory, the global potential canopy cover may shrink by ~223 million hectares by 2050, with the vast majority of losses occurring in the tropics. Our results highlight the opportunity of climate change mitigation through global tree restoration but also the urgent need for action.

The global tree restoration potential.

Tamm Review: Influence of forest management activities on soil organic carbon stocks: A knowledge synthesis

Combining global tree cover loss data with historical national forest cover maps to look at six decades of deforestation and forest fragmentation in Madagascar

We investigate the causes of deforestation in Indonesia, a country with one of the highest rates of primary natural forest loss in the tropics, annually between 2001 and 2016. We use high spatial resolution imagery made available on Google Earth to characterize the land cover types following a random selection of deforestation events, drawn from the Global Forest Change dataset. Notorious in the region, large-scale oil palm and timber plantations together contributed more than two-fifths of nationwide deforestation over our study period, with a peak in late aughts followed by a notable decline up to 2016. Conversion of forests to grasslands, which comprised an average of one-fifth of national deforestation, rose sharply in dominance in years following periods of considerable fire activity, particularly in 2016. Small-scale agriculture and small-scale plantations also contributed one-fifth of nationwide forest loss and were the dominant drivers of loss outside the major islands of Indonesia. Although relatively small contributors to total deforestation, logging roads were responsible for a declining share of deforestation, and mining activities were responsible for an increasing share, over the study period. Direct drivers of deforestation in Indonesia are thus spatially and temporally dynamic, suggesting the need for forest conservation policy responses tailored at the subnational level, and new methods for monitoring the causes of deforestation over time.

https://iopscience.iop.org/article/10.1088/1748-9326/aaf6db/pdf

What causes deforestation in Indonesia

. Land-use and land-cover change (LULCC) impacts local energy and
water balance and contributes on global scale to a net carbon
emission to the atmosphere. The newly released annual ESA CCI (climate change initiative) land
cover maps provide continuous land cover changes at 300  m 
resolution from 1992 to 2015, and can be used in land surface models
(LSMs) to simulate LULCC effects on carbon stocks and on surface
energy budgets. Here we investigate the absolute areas and gross and
net changes in different plant functional types (PFTs) derived from
ESA CCI products. The results are compared with other
datasets. Global areas of forest, cropland and grassland PFTs from
ESA are 30.4, 19.3 and 35.7 million  km2 in the year 2000. The
global forest area is lower than that from LUH2v2h (Hurtt et al.,
2011), Hansen et al. (2013) or Houghton and Nassikas (2017) while
cropland area is higher than LUH2v2h (Hurtt et al., 2011), in which
cropland area is from HYDE 3.2 (Klein Goldewijk et al., 2016). Gross
forest loss and gain during 1992–2015 are 1.5 and
0.9 million  km2 respectively, resulting in a net forest
loss of 0.6 million  km2 , mainly occurring in South and
Central America. The magnitudes of gross changes in forest, cropland
and grassland PFTs in the ESA CCI are smaller than those in other
datasets. The magnitude of global net cropland gain for the whole
period is consistent with HYDE 3.2 (Klein Goldewijk et al., 2016),
but most of the increases happened before 2004 in ESA and after
2007 in HYDE 3.2. Brazil, Bolivia and Indonesia are the countries
with the largest net forest loss from 1992 to 2015, and the
decreased areas are generally consistent with those from Hansen
et al. (2013) based on Landsat 30  m resolution
images. Despite discrepancies compared to other datasets, and
uncertainties in converting into PFTs, the new ESA CCI products
provide the first detailed long-term time series of land-cover change and
can be implemented in LSMs to characterize recent carbon dynamics,
and in climate models to simulate land-cover change feedbacks on
climate. The annual ESA CCI land cover products can be downloaded
from http://maps.elie.ucl.ac.be/CCI/viewer/download.php (Land
Cover Maps – v2.0.7; see details in Sect. 5). The PFT map
translation protocol and an example in 2000 can be downloaded from
 https://doi.org/10.5281/zenodo.834229 . The annual ESA CCI PFT maps from
1992 to 2015 at 0.5 ∘ × 0.5 ∘ resolution can
also be downloaded from https://doi.org/10.5281/zenodo.1048163 .

/pdf/gross-and-net-land-cover-changes-in-the-main-plant-3e54qpaewk.pdf

Gross and net land cover changes in the main plant functional types derived from the annual ESA CCI land cover maps (1992–2015)

Dryland biomes cover two-fifths of Earth’s land surface, but their forest area is poorly known. Here, we report an estimate of global forest extent in dryland biomes, based on analyzing more than 210,000 0.5-hectare sample plots through a photo-interpretation approach using large databases of satellite imagery at (i) very high spatial resolution and (ii) very high temporal resolution, which are available through the Google Earth platform. We show that in 2015, 1327 million hectares of drylands had more than 10% tree-cover, and 1079 million hectares comprised forest. Our estimate is 40 to 47% higher than previous estimates, corresponding to 467 million hectares of forest that have never been reported before. This increases current estimates of global forest cover by at least 9%.

/pdf/the-extent-of-forest-in-dryland-biomes-2on8lyi2ty.pdf

The extent of forest in dryland biomes

Combining community needs and preferences with dryland plant expertise in order to select suitable native species for
large-scale natural capital restoration is the approach that has been successful in the Sahel as part of Africa’s Great Green
Wall program. In order to increase plant diversity and restore degraded land, we investigated four cross-border regions of
Mali, Burkina Faso, and Niger, all located in dryland ecosystems of the Sahel. In 120 beneficiary village communities, with
a total population of over 50,000 farmers, including 51% women, participatory diagnostic meetings were conducted, leading
to the selection of 193 plant species, most of which were mainly used for food, medicine, fodder, and fuel. Of these, 170 were
native and considered suitable for enriching and restoring those village lands. The most environmentally well-adapted and
economically relevant species were prioritized, quality seeds were collected, and nursery seedlings produced under technical
supervision of villages. From 2013 to 2015, 55 woody and herbaceous species were planted to initiate restoration of 2,235 ha of
degraded land. On average, 60% of seedlings survived and grew well in the field after three rainy seasons. Due to its multiple
uses, including gum arabic production, Acacia senegal was preferred by local people in most cases, accounting for 30% of
seedlings planted. Such promising results, in an effort to restore degraded land for and with the help of thousands of farmers,
could not have been achieved without the combination of scientific plant expertise and efficient rural capacity development,
underpinned by high levels of community engagement.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/rec.12337

Community participation and ecological criteria for selecting species and restoring natural capital with native species in the Sahel

Reflecting on twenty years of forest landscape restoration

The Great Green Wall for the Sahara and the Sahel Initiative was launched to address the increasing challenges of land degradation, desertification and drought, climate change, food insecurity and poverty in more than 20 countries. Restoration of agro-sylvo-pastoral landscapes and degraded lands is one of the priority interventions initiated, enabling the springing up of green nests of life. When complete, the Great Green Wall of Africa will reverse the seemingly unstoppable desertification and address the development of its drylands’ inhabitant rural communities. Today’s planting of modest seedlings will grow into vast mosaics of forest and agroforestry landscapes and grasslands, which will provide essential ecosystem goods and services, restore lost livelihoods and create new wealth. The ambition of reforestation efforts within this initiative ‐ the like of which the world has never seen before ‐ sounds like an impossible dream. However, learning from past mistakes and capitalising on current advancement in science and technology, it is a reality that is taking root. Following a successful restoration model that RBG Kew experts have devised, we are helping to mobilise, train and support communities in four border regions in Burkina Faso, Mali and Niger. In collaboration with FAO, the Millennium Seed Bank Partnership is using its unique expertise to ensure that seeds of environmentally well-adapted and economically useful local species are collected and planted in communal gardens and village agroforestry systems managed by the communities themselves. In our first year, an estimated total of 162,000 seedlings and 61 kg of seeds from 40 useful native species, including grasses for livestock, have been planted to cover 237 ha of farmer-managed land in 19 villages. The keen interest it has created has indicated that these figures will rise five-fold in the second year. These green bricks are the foundations of the living wall that will eventually reach across the Sahel and beyond.

/pdf/africa-s-great-green-wall-initiative-a-model-for-restoration-46usw1qson.pdf

Nora Berrahmouni

Papers

The extent of forest in dryland biomes

Community participation and ecological criteria for selecting species and restoring natural capital with native species in the Sahel

Reflecting on twenty years of forest landscape restoration

Africa's Great Green Wall Initiative: a model for restoration success