"Is Africa’s Great Green Wall project withering?"

I say: Let it wither. It's a threat to the Sudano-Sahelian & Moist Combretum-Terminalia savannas.

Will the scientists who "have the task of mapping carbon (including carbon sequestration) and biodiversity in the world’s tropical forests in the next five years" continue to misclassify #TropicalGrassyBiomes as 'forest', 'deforested' or 'degraded forest' as they continue to use FAO's outdated definition of forest.

https://www.nature.com/articles/d41586-023-01293-6

The FAO’s definition of #forest is based on tree height > 5 m and tree cover > 10%. They introduced the definition in 1980, based on UNESCO’s 'International classification and mapping of vegetation' published in 1973. The FAO’s definition has persisted for > 4 decades despite being outdated and leading to #TropicalGrassyBiomes (savannas) being falsely classified as ‘forest’, 'degraded forest' or 'deforested'.

#SavannasMatter

#TropicalGrassyBiomes like the #Cerrado of South America are under threat of degradation by #Forestization.

Stop large-scale #TreePlanting in #GrassyBiomes. #Savannas are NOT "degraded forests".

Stop mapping global "forests" in terms of vegetation height and woody cover alone. That leads to misclassification of savannas as #forests.

#SavannasMatter

https://news.mongabay.com/2023/04/to-restore-brazils-cerrado-planting-trees-is-a-bad-option-experts-say/

@TobiasKuemmerle
Interesting analysis, but depends heavily on how deforestation is defined and the ability to differentiate between forest, degraded forest and #TropicalGrassyBiomes (i.e. savannas). They acknowledge the inability to differentiate between forest and agro-forests, but not between degraded forest and savanna. Use of Hansen et al's (2013) Global Forest Change data is problematic because forest is defined as >50 % crown cover of trees taller than 5 m height.

#SavannasMatter

Savannas are perpetually misclassified as forests.
https://besjournals.onlinelibrary.wiley.com/doi/epdf/10.1111/2041-210X.14040

Savannas like longleaf pine savanna in Florida are not "forested ecosystems". They are #TropicalGrassyBiomes whose plants are adapted fire.

#SavannasMatter

https://onlinelibrary.wiley.com/doi/epdf/10.1111/aec.13283

Great piece of #SavannaScience work by Corli Wigley-Coetsee and others showing factors other than large mammal herbivory, such as dispersal limitation, seed predation, or drought, may limit woody plant populations and communities in semi-arid #TropicalGrassyBiomes.

@marijnvdpas

News headlines like this create a negative perception of savannas in the eyes of the general public.

I can't read the whole NYT article, but I guess it's based on the recent paper in PNAS 119(52), e2203200119, which I have yet to read thoroughly, but my first impression was mixed. On the downside, portraying #TropicalGrassyBiomes as a stage in linear succession from grassland to forest is outdated, misleading and ignores current thinking in #SavannaScience.

#SavannasMatter

@hakim

Excellent review of satellite remote sensing for mapping #GrassyBiomes at regional and global scales.

This is crucial for #SavannaScience and the prevention of #Forestization of #OpenNaturalEcosystems such as #TropicalGrassyBiomes.

The EU and FAO need to read this, and other recent related work, and then realise they need to update their antiquated definition of "forest" based only on veg structure and ignoring #FunctionalTraits.

#SavannasMatter

This grabbed my attention.
https://www.nature.com/articles/s41597-022-01774-9.

I recently compiled data on leaf area. I was keen to compare for species with bipinnate compound leaves that are common in African #TropicalGrassyBiomes. For leaf area I used leaflet size from https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:77089275-1/general-information.

I downloaded their data (https://doi.org/10.17871/TRY.81). The metadata says leaf area is "in case of compound leaves the area of a leaflet lamina". I checked Acacia nilotica. Theirs: 1691.79 mm^^. Mine: 4.2 mm^^.

#FunctionalTraits

This grabbed my attention.
https://www.nature.com/articles/s41597-022-01774-9.

I recently compiled data on leaf area. I was keen to compare for species with bipinnate compound leaves that are common in African #TropicalGrassyBiomes. For leaf area I used leaflet size from https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:77089275-1/general-information.

I downloaded their data (https://doi.org/10.17871/TRY.81). The metadata says leaf area is "in case of compound leaves the area of a leaflet lamina". I checked Acacia nilotica. Theirs: 1691.79 mm^^. Mine: 4.2 mm^^.

#FunctionalTraits

It's time we stopped referring to fire and herbivores as 'disturbances' in #SavannaScience.

They are important *consumers* in #TropicalGrassyBiomes, and savanna plants are adapted to them.

#SavannasMatter

3/3

Then, saying "a linear relationship between AGB and Landsat 8 derived spectral variables" is a suitable approach "for monitoring and reporting of biomass baselines in low-biomass, open canopy woodlands for REDD+ projects" is the last straw for me, and others in #SavannaScience.

#TropicalGrassyBiomes are not "forests" and they are not "degraded forests". This mindset (especially when it leads to fire-suppression and tree planting) is what leads to degraded savannas.

#SavannasMatter

2/n

Saying that "wildfires and a high density of mega-herbivores ... have a significant impact on tree cover and structural diversity by modifying vegetation structure through grazing and physical damage,
thereby making trees less tolerant to fire.." is not incorrect, but to say fire and herbivory are "degrading dryland forests" completely misses the role these consumers play in maintaining southern African #TropicalGrassyBiomes.

#SavannasMatter

1/n

This is beyond cringe-worthy for anyone in #SavannaScience to read:

https://www.sciencedirect.com/science/article/pii/S0034425722003388?via%3Dihub

"Dryland forests in Southern Africa are currently experiencing high rates of forest loss as a result of overexploitation, wildfire, and herbivory..." is misleading.

There are no "dryland forests" in southern Africa. What they are referring to are #TropicalGrassyBiomes, where fire and herbivory are crucial.

#SavannasMatter

@bjenquist

Agreed. Huge disparities in 'global' biodiversity data demand attention.

The geographical biases in plant functional trait data are also a concern. For example, functional traits of #WoodyPlants in #TropicalGrassyBiomes are under-sampled.

#SavannasMatter
#SavannaScience

1/2

Great new contribution to #SavannaScience here:

https://nph.onlinelibrary.wiley.com/doi/10.1111/nph.18648

Rico Holdo and Jesse Nippert argue that tree dominance in #TropicalGrassyBiomes is "precluded by ecohydrological constraints in dry savannas, and by fire and herbivores in wet savannas. Strong asymmetric grass-tree competition for soil moisture limits tree growth, exposing trees to persistent demographic bottlenecks."

The descriptions and maps of #TropicalGrassyBiomes in the IUCN Global Ecosystem Typology (v2.1) are an excellent resource.

https://global-ecosystems.org/explore/biomes/T4

#SavannasMatter

They are not based on the FAO's outdated definitions that perpetuate the misclassification of savannas as "forest" or "degraded forest".

#SavannaScience

They are based on current thinking about #OpenBiomes /
#OpenNaturalEcosystems in the framework of #AlternateBiomeStates.

https://www.sciencedirect.com/science/article/pii/S0169534722000611?via%3Dihub

"Due to its vast landmass and unique ecosystems, Africa has the potential to contribute significantly to land-based mitigation and adaptation interventions, offering an estimated 21% of global potential for increased carbon storage on land."

https://www.researchgate.net/publication/365623489_Policy_Brief_Finding_a_way_forward_for_Nature-based_Solutions_in_Africa's_grassy_ecosystems

#Forestization threatens #TropicalGrassyBiomes.