Land cover change and carbon emissions over 100 years in an African biodiversity hotspot

Simon Willcock, Oliver L. Phillips, Philip J. Platts, Ruth D. Swetnam, Andrew Balmford, Neil D. Burgess, Antje Ahrends, Julian Bayliss, Nike Doggart, Kathryn Doody, Eibleis Fanning, Jonathan Michael Halsey Green, Jaclyn Hall, Kim L. Howell, Jon C. Lovett, Robert Marchant, Andrew R. Marshall, Boniface Mbilinyi, Pantaleon K T Munishi, Nisha OwenElmer J. Topp-Jorgensen, Simon L. Lewis

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Agricultural expansion has resulted in both land use and land cover change (LULCC) across the tropics. However, the spatial and temporal patterns of such change and their resulting impacts are poorly understood, particularly for the pre-satellite era. Here we quantify the LULCC history across the 33.9 million ha watershed of Tanzania's Eastern Arc Mountains, using geo-referenced and digitised historical land cover maps (dated 1908, 1923, 1949 and 2000). Our time series from this biodiversity hotspot shows that forest and savanna area both declined, by 74% (2.8 million ha) and 10% (2.9 million ha), respectively, between 1908 and 2000. This vegetation was replaced by a five-fold increase in cropland, from 1.2 million ha to 6.7 million ha. This LULCC implies a committed release of 0.9 Pg C (95% CI: 0.4-1.5) across the watershed for the same period, equivalent to 0.3 Mg C ha(-1) yr(-1) . This is at least three-fold higher than previous estimates from global models for the same study area. We then used the LULCC data from before and after protected area creation, as well as from areas where no protection was established, to analyse the effectiveness of legal protection on land cover change despite the underlying spatial variation in protected areas. We found that, between 1949 and 2000, forest expanded within legally protected areas, resulting in carbon uptake of 4.8 (3.8-5.7) Mg C ha(-1) , compared to a committed loss of 11.9 (7.2-16.6) Mg C ha(-1) within areas lacking such protection. Furthermore, for nine protected areas where LULCC data is available prior to and following establishment, we show that protection reduces deforestation rates by 150% relative to unprotected portions of the watershed. Our results highlight that considerable LULCC occurred prior to the satellite era, thus other data sources are required to better understand long-term land cover trends in the tropics. This article is protected by copyright. All rights reserved.

Original languageEnglish
Pages (from-to)2787–2800
Number of pages14
JournalGlobal Change Biology
Issue number8
Early online date8 Jan 2016
Publication statusPublished - 2016

Bibliographical note

This article is protected by copyright. All rights reserved. This is an author produced version of a paper published in Global Change Biology. Uploaded in accordance with the publisher's self-archiving policy.


  • afforestation
  • deforestation
  • land use change
  • protected area
  • reforestation
  • carbon
  • emission
  • ecosystem service

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