Protected area management effectiveness is pivotal in nature-based solutions for carbon neutrality: A tale from the Eastern Arc Mountains, Tanzania

• The rate of carbon sequestration varies between forest cover and protected area (PA) categories. • The stock differencing and stump inventory methods yield non-statistically significant estimates of rates of carbon emission. • Stable forests in PA I contribute significantly (>80 %) to carbon sequestration compared to PA IV and other land uses. • Deforestation is the prominent driver of emissions both in PAs and in other land uses. • PA management effectiveness is pivotal in nature-based solutions. The study evaluated the pivotal role of protected area management effectiveness in Nature-based Solutions for carbon neutrality in the Eastern Arc Mountains (EAMs), Tanzania. To achieve its objective, the study compared land cover and land use, and carbon dynamics between PA category I, PA category IV and other land uses (10 km divided into 5 km segments) around the PAs. The study revealed that, PA category I is a net carbon sink for the period 1995–2020, while PA category IV and other land uses show mixed results for the same period. In some instances, they are net carbon sinks, while in some instances, the PA category IV and other land uses are net carbon sources. Net carbon sink in PA category I, and its buffers I and II were, on average, −5.56 million, −1.73 million and −0.48 million megagrams of CO 2 equivalent annually, respectively. Similarly, the net carbon sink in PA category IV, and its buffers I and II, was on average, −0.72 million, −0.45 million and −0.26 million megagrams of CO 2 equivalent annually, respectively. The net carbon sink was due to a high rate of carbon sequestration as a result of tree growth and recruitment in stable forests, forest appreciation and forest gain and on the other hand, it was due to low carbon emissions through deforestation and forest degradation. These findings underscore empirically the critical role of PA management effectiveness in restricting anthropogenic forest degradation and loss, and on the other hand, promote forest restoration and appreciation. Hence, serving as nature-based solutions that significantly contribute to addressing carbon neutrality goals and other multifaceted environmental, economic and societal challenges. This study contributes to the methodological approaches of accounting for forest carbon degradation and extends knowledge on the evaluation of PA management effectiveness and PA policies. It also supports national and sub-national nature-based solution action planning.