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What exactly is "Land-Use Change and Forestry" and why is it sometimes hugely positive (Indonesia) but sometimes hugely negative (China)? Isn't it supposed to be a type of source, not sink (you cut trees, you get more GHG)? See the data here.

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  • $\begingroup$ you can also plant trees or re-vegetate $\endgroup$
    – f.thorpe ♦
    Jun 20, 2021 at 21:06

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You are correct that normally you see a net positive value of GHGs from land use change. However, if forests are grown or revegetated, it is considered a sink (and negative GHG value). This paper says that China has undergone a net increase in forest.
The results sections says:

The land-use data derived from Landsat Thematic Mapper (TM) imagery from 1990 to 2010 were used to estimate the spatiotemporal dynamics of land-use and carbon storage change.

and

Between 1990 and 2010, China experienced a net increase in forestland, farmland, urban land, and other land (sandy land, gobi, saline-alkali land, swampland, bareland, rock and gravel, and other unused land; table S1). The magnitudes of these increases were 1.52 × 106ha (+0.7%), 1.48 × 106ha (+0.8%),6.87 × 106ha (+43.0%), and 11.74 × 106ha (+5.8%), respectively.

and

Over the last few decades, the Chinese government developed a number of afforestation programs to revert historically forested areas that had previously been converted into farmland back to forest. Programs, such as the Slope Land Conversion Project and the Natural Forest Protection Project, were responsible for the increases in the area of forest in most regions, except Northeast and Northwest China.

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  • $\begingroup$ Ok, but Russia doesn't plant trees on a large scale. On the contrary, loads of trees are burnt and cut down. Why is the Russian figure also so negative? $\endgroup$
    – Sergey Zolotarev
    Jun 21, 2021 at 7:58
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    $\begingroup$ @SergeyZolotarev It's because the vast existing forests in Russia are a net C sink. For example, Russia reported to UNFCCC for 2018 net sinks of 658 MtCO2 for existing forest and 16 MtCO2 for land converted to forest. The 124 MtCO2 from forest fire is already subtracted from that first number, but a 16 MtCO2 biomass change from logging is dealt with separately. $\endgroup$
    – Deditos
    Jun 21, 2021 at 10:43
  • $\begingroup$ @Deditos Why is it dealt with separately? $\endgroup$
    – Sergey Zolotarev
    Jun 22, 2021 at 3:42
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    $\begingroup$ @SergeyZolotarev It still comes under the LULUCF sector, but it has its own category. Wood products are effectively separate reservoirs that are subject to imports/exports and have their own decay/emission rates (more info). $\endgroup$
    – Deditos
    Jun 22, 2021 at 11:28

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