Christmas came early this year, thanks to the World Resources Institute and their tool to “play” with: the water module of the Global Forest Watch (GFW). This tool provides forest-related insights at watershed levels, reflecting the importance of trees in the fight against climate change, soil erosion and desertification. The tool has actually been available since August. Below are my top insights when I was “playing” with it.
Trees can play a key role in protecting water resources
A reminder first. Trees and more generally vegetation matter for water quality and quantity. Indeed, forests can improve groundwater recharge and soil moisture holding capacity, reduce surface runoff, as well as reduce sediments and increase dissolved oxygen in water streams. These benefits add on to the role of forests in fighting soil erosion, desertification and climate change. This being said, the type of trees and their locations should be carefully selected for reforestation not to be counterproductive and damaging, rather than protecting water resources. The table below summarizes some potential benefits and negative impacts of forests.
GFW imaging clearly shows China has two lungs
With the Global Forest Watch one can look at the existing global tree cover. The imaging or “X-ray” clearly shows China’s two lungs: a Southern one in the Yangtze River basin (YRB) and Pearl River basin (PRB), and a Northern one in the Amur River basin. See map below.
GFW shows China has two lungs – one Northern in the Amur River Basin & one Southern in the YRB & PRB
(Click image to enlarge)
Deforestation in China is slowing down
There is some disagreement on whether or not global deforestation has been accelerating or decelerating recently. As for China, there seems to be more consensus on positive trends, where reforestation is estimated to have outpaced deforestation.
The GFW details the evolution of tree cover loss in China from 2000 to 2014. The numbers show a decrease in deforestation rate since 2008 and more markedly since 2012. Note, this does not account for the forest gains elsewhere. However different research methodologies prevent us from comparing the numbers and compute a net loss.
Data shows a decrease in deforestation rate since 2008 & more markedly since 2012
This progress may be partially ascribed to the ongoing policies such as the logging bans in natural forests upstream of the Yangtze River, the upstream and middle stream of the Yellow River (since 2000) and in the key state-owned natural forests in the North East regions (reduced logging since 2000, actual ban since 2014). The effectiveness of such policies can indirectly be confirmed when looking at borders.
Trees beyond borders: jurisdiction matters
Satellite imaging ignores borders and therefore offer more robust comparisons than national statistics do. Given the usual skepticism around China’s national official numbers (not to mention other countries), such transparency and consistency should be warmly welcomed.
Deforestation rates often vary significantly from one side of a border to the other…
…policy & regulatory schemes do have an impact
Glancing here and there at countries’ borders, one can notice that deforestation rates often vary significantly from one side of a border to the other. We looked for instance at the border between Russia and China (see below; click to enlarge), more precisely between Russia and China’s Heilongjiang province where commercial logging in state-owned natural forests has officially been halted. The significantly lower deforestation rate on the China’s side suggests that jurisdiction matters and that policy and regulatory schemes do have an impact. Note that to be more accurate, a deeper analysis should also look at the different economic conditions across the border.
As mentioned earlier, tree cover losses can have harmful impacts on water resources. This is why WRI developed the recently released water module that allows us to conduct watershed level analyses.
Diverse risks for diverse watersheds
In the Water module of the GFW, one can look at watersheds individually and the salience of four different “watershed risks”, namely recent forest loss, historical forest loss, erosion risk and fire risk (see an example of watershed factsheet for more details).
Different river basins are exposed to different risks, such as historical deforestation & soil erosion
At a glance, the Yellow River Basin seems to have been mainly impacted by historical deforestation (prior to 2000) whilst the Yangtze River Basin is mainly exposed to soil erosion risks. Such risks’ snapshots are automatically generated and may therefore lack more granular/qualitative considerations. However, they provide a great place to start with for comparing the state of forests and soils in China’s watersheds and beyond.
Not the same story across different data sources
Unfortunately, different datasets using different methodologies do not all show she same picture. The tree cover estimations in the GFW are based on satellite imagery at a 30-meter spatial resolution, as part of a collaboration between University of Maryland, Google, USGS, and NASA. In this dataset, tree cover is defined as “all vegetation greater than 5 meters in height, and may take the form of natural forests or plantations across a range of canopy densities”.
Other studies have used different approaches, relying for instance on surface reflectance data rather than land imageries. As shown in the maps below (click to enlarge), results can differ quite significantly.
But tree cover picture can vary depending on methodology & data used
The study using reflectance data (right-hand side) found much more significant reforestation, particularly in central China. Such discrepancy casts some doubts on the results’ accuracy, and unless you’re a remote sensing expert, there is little chance for you to know which one to trust. Yet this should not prevent us from making the best use of these new mines of information that are offered to us.
“Wielding data for change”
The GFW is extremely valuable to glance at the impact our society is having on our forests. Thanks to WRI and its partners, it is now extremely convenient for everyone to investigate these issues. Ultimately, the proliferation of mapping tools, be it on forests, water or supply chains, should allow all of us to better understand the ongoing environmental changes, locally and globally, here and there and what the trends are like.
Data is now pouring in from many sources; we should use it to build more compelling cases for change
Mapping is just a start however. As data is now pouring down from satellites and other sources, we, as dedicated NGOs, scientists, journalists, or activists should use it to build ever more compelling cases for change, and provide with ever more actionable information for the various parties. “Wielding data for change” might be a relevant motto for 2017.
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