Tropical forests store roughly half of the world's forest carbon stocks, acting as carbon sinks through a positive balance of tree growth, recruitment and mortality (Pan et al., 2011). While forest carbon stocks and sinks in the tropics have mainly been studied in structurally intact, undisturbed forests in humid ecosystems (Brienen et al., 2015; Hubau et al., 2020; Qie et al., 2017), disturbed and recovering forests are both increasing in extent (Aide et al., 2013; Lewis et al., 2015). In this respect, understanding and quantifying forest carbon stocks and sinks in disturbed or recovering forests is essential to realistically represent the current role of tropical forests within the global carbon cycle.
Here, we will showcase two examples in which remote sensing of forest dynamics using the Landsat archive and national forest inventory data are integrated to contribute towards the understanding and estimation of aboveground forest carbon stocks and sinks in tropical forests and woodlands. The first example, published in 2021 (Requena Suarez et al., 2021), integrates Tanzania’s national forest inventory data on forest carbon stocks with information on time since establishment obtained from satellite time series of forest cover. The objectives of this study are twofold: (1) explore the carbon sink capacity of Tanzania’s recovering forest and woodlands and (2) identify the environmental and anthropogenic drivers of carbon stocks in these forest ecosystems. The second example, currently under preparation, integrates Peru’s national forest inventory data on forest carbon stocks and biodiversity with information on time and intensity of disturbance obtained from satellite time series of a vegetation index (NDMI; Normalized Difference Moisture Index) in Peruvian Amazonia.
This study seeks to (1) evaluate the degree of forest disturbance in Peruvian Amazonia; (2) assess the effects of disturbance intensity and time since disturbance on carbon stocks, biodiversity and their recovery; and (3) identify the main drivers of biomass and biodiversity in disturbed forests.
Until now, largescale estimates had been lacking for both recovering dry forests and woodlands in south-eastern Africa, as well as disturbed humid forests in Peruvian Amazonia. Both examples produce estimates of carbon stock and sinks which can be applied in national or regional (Tier 2) levels of IPCC reporting. In addition, the use of existing spatial data on climate, soil fertility, human accessibility and surrounding forest cover were used to test the effects of environmental gradients and variations in human use. In this respect, large-scale assessments of recovering and disturbed forests that combine space-based forest dynamics data with national forest inventories and spatial datasets can aid in the derivation of estimates better reflect the reality of natural forests across large areas in terms of carbon stocks and sinks, as well as address knowledge gaps regarding the main drivers behind forest carbon stocks. In this respect, we expect insights derived from both examples to be used in the characterisation of disturbed and recovering forests, mainly in connection to landscape conservation and restoration planning.
Aide, T. M., Clark, M. L., Grau, H. R., López-Carr, D., Levy, M. A., Redo, D., Bonilla-Moheno, M., Riner, G., Andrade-Núñez, M. J., & Muñiz, M. (2013). Deforestation and Reforestation of Latin America and the Caribbean (2001-2010). Biotropica, 45(2), 262–271. https://doi.org/10.1111/j.1744-7429.2012.00908.x
Brienen, R. J. W., Phillips, O. L., Feldpausch, T. R., Gloor, E., Baker, T. R., Lloyd, J., Lopez-Gonzalez, G., Monteagudo-Mendoza, A., Malhi, Y., Lewis, S. L., Vasquez Martinez, R., Alexiades, M., Alvarez Davila, E., Alvarez-Loayza, P., Andrade, A., Aragao, L. E. O. C., Araujo-Murakami, A., Arets, E. J. M. M., Arroyo, L., … Zagt, R. J. (2015). Long-term decline of the Amazon carbon sink. Nature, 519(7543), 344–348. https://doi.org/10.1038/nature14283
Hubau, W., Lewis, S. L., Phillips, O. L., Affum-Baffoe, K., Beeckman, H., Cuní-Sanchez, A., Daniels, A. K., Ewango, C. E. N., Fauset, S., Mukinzi, J. M., Sheil, D., Sonké, B., Sullivan, M. J. P., Sunderland, T. C. H., Taedoumg, H., Thomas, S. C., White, L. J. T., Abernethy, K. A., Adu-Bredu, S., … Hemisphere, N. (2020). Asynchronous carbon sink saturation in African and Amazonian tropical forests. Nature, 579(7797), 80–87. https://doi.org/10.1038/s41586-020-2035-0
Lewis, S. L., Edwards, D. P., & Galbraith, D. (2015). Increasing human dominance of tropical forests. Science (New York, N.Y.), 349(6250), 827–832. https://doi.org/10.1126/science.aaa9932
Pan, Y., Birdsey, R. A., Fang, J., Houghton, R., Kauppi, P. E., Kurz, W. A., Phillips, O. L., Shvidenko, A., Lewis, S. L., Canadell, J. G., Ciais, P., Jackson, R. B., Pacala, S. W., McGuire, A. D., Piao, S., Rautiainen, A., Sitch, S., & Hayes, D. (2011). A Large and Persistent Carbon Sink in the World’s Forests. Science, 333(6045), 988–993. https://doi.org/10.1126/science.1204588
Qie, L., Lewis, S. L., Sullivan, M. J. P., Lopez-Gonzalez, G., Pickavance, G. C., Sunderland, T., Ashton, P., Hubau, W., Abu Salim, K., Aiba, S., Banin, L. F., Berry, N., Brearley, F. Q., Burslem, D. F. R. P., Dančák, M., Davies, S. J., Fredriksson, G., Hamer, K. C., Hédl, R., … Phillips, O. L. (2017). Long-term carbon sink in Borneo’s forests halted by drought and vulnerable to edge effects. Nature Communications, 8(1), 1966. https://doi.org/10.1038/s41467-017-01997-0
Requena Suarez, D., Rozendaal, D. M. A., De Sy, V., Gibbs, D. A., Harris, N. L., Sexton, J. O., Feng, M., Channan, S., Zahabu, E., Silayo, D. S., Pekkarinen, A., Martius, C., & Herold, M. (2021). Variation in aboveground biomass in forests and woodlands in Tanzania along gradients in environmental conditions and human use. Environmental Research Letters, 16(4), 44014. https://doi.org/10.1088/1748-9326/abe960