Quantifying the spatial patterns of Secondary Forest carbon sequestration potential in the Brazilian Amazon
Authors: Heinrich Viola , Dalagnol Ricardo , Cassol Henrique , Rosan Thais , Torres de Almeida Catherine , Silva Junior Celso , Campanharo Welsey , House Joanna , Sitch Stephen , Hales Tristram , Adami Marcos , Anderson Liana , Aragão Luiz 
Published: March 2021

&lt;p&gt;Overall, global forests are expected to contribute about a quarter of pledged mitigation under the Paris Agreement, by limiting deforestation and by encouraging forest regrowth.&lt;/p&gt;&lt;p&gt;Secondary Forests in the Neo-tropics have a large climate mitigation potential, given their ability to sequester carbon up to 20 times faster than old-growth forests. However, this rate does not account for the spatial patterns in secondary forest regrowth influenced by regional and local-scale environmental and anthropogenic disturbance drivers.&lt;/p&gt;&lt;p&gt;Secondary Forests in the Brazilian Amazon are expected to play a key role in achieving the goals of the Paris Agreement, however, the Amazon is a large and geographically complex region such that regrowth rates are not uniform across the biome.&lt;/p&gt;&lt;p&gt;To understand the impact of key drivers we used a multi-satellite data approach with the aim of understanding the spatial variations in secondary forest regrowth in the Brazilian Amazon. We mapped secondary forest area and age using a land-use-land-cover dataset &amp;#8211; MapBiomas &amp;#8211; and, combined with the European Space Agency Aboveground Carbon dataset, constructed regional regrowth curves for the year 2017.&lt;/p&gt;&lt;p&gt;We found large variations in the regrowth rates across the Brazilian Amazon due to large-scale environmental drivers such as rainfall and shortwave-radiation. Regrowth rates are similar to previous pan-Amazonian estimates in the North-West (3 &amp;#177;1.0 MgC ha&lt;sup&gt;-1&lt;/sup&gt; yr&lt;sup&gt;-1&lt;/sup&gt;), which are double than those in the North-East Amazon (1.3 &amp;#177;0.3 MgC ha&lt;sup&gt;-1&lt;/sup&gt; yr&lt;sup&gt;-1&lt;/sup&gt;). The impact of anthropogenic disturbances, namely fire and repeated deforestation prior to the most recent regrowth only reduces the regrowth by 20% in the North-West (2.4 &amp;#177;0.8 MgC ha&lt;sup&gt;-1&lt;/sup&gt; yr&lt;sup&gt;-1&lt;/sup&gt;) compared to 55% in the North-East (0.8 &amp;#177;0.8 MgC ha&lt;sup&gt;-1&lt;/sup&gt; yr&lt;sup&gt;-1&lt;/sup&gt;). Overall, secondary forest carbon stock of 294 TgC in the year 2017, could have been 8% higher with avoided fires and repeat deforestation.&lt;strong&gt; &lt;/strong&gt;We found that the 2017 area of secondary forest, which occupies only ~4% of the Brazilian Amazon biome, can contribute significantly (~5.5%) to Brazil&amp;#8217;s net emissions reduction targets, accumulating ~19.0 TgC yr&lt;sup&gt;-1&lt;/sup&gt;until 2030 if the current area of secondary forest is maintained (13.8 Mha). However,this value reduces rapidly to less than 1% if only secondary forests older than 20 years are preserved (2.2 Mha).&lt;/p&gt;&lt;p&gt;Preserving the remaining old-growth forest carbon stock and implementing legal mechanisms to protect and expand secondary forest areas are key to realising the potential of secondary forest as a nature-based climate change mitigation solution.&lt;/p&gt;