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    Division BEE  >  Biodiversity & Ecology  >  Vol.6 >  Article 5.1

Biodiversity & Ecology

 Food security    Research article    Open Access 

Deforestation for agricultural expansion in SW Zambia and NE Namibia and the impacts on soil fertility, soil organic carbon- and nutrient levels


Marleen de Blécourt, Achim Röder, Alexander Gröngröft*, Stephan Baumann, David Frantz, Annette Eschenbach

Article first published online: 24 April 2018

DOI: 10.7809/b-e.00330

*Corresponding author contact: alexander.groengroeft@uni-hamburg.de

Biodiversity & Ecology  (Biodivers. Ecol.)

Climate change and adaptive land management in southern Africa - assessments, changes, challenges, and solutions,
edited by Rasmus Revermann, Kristin M. Krewenka, Ute Schmiedel, Jane M. Olwoch, Jörg Helmschrot & Norbert Jürgens
Volume 6, pages 242-250, April 2018
  PDF  (1.9 MB)

English

Abstract: In southern African drylands, an important driver of deforestation is the ongoing conversion of woodland to smallholder agriculture. Our study in NE Namibia and SW Zambia evaluated the potential of operational earth observation satellites to characterize land-use change processes and quantifi ed their impact on soil organic carbon (SOC) and nutrient concentrations. We found that the area under agricultural use increased by 24% from 2002 to 2013, mainly at the expense of natural vegetation (i.e., woodland). This conversion caused a decline in SOC and total N and tended to increase plantavailable P in the soils of old agricultural fi elds. The eff ects were most pronounced in NE Namibia, where the total SOC stocks were 19.6% (±18.4 SD) lower in agricultural land compared to woodland. Moreover, the losses in SOC and total N tended to result in a decline of predicted maize yields calculated with the QUEFTS model by ~15% when comparing soils of old agricultural fi elds and woodland. Overall, our results indicate that long-term continuation of low-input arable farming can reduce soil fertility.

Portuguese

Resumo: Nas terras áridas da África Austral, a conversão contínua de fl oresta para agricultura de subsistência é um factor importante de desfl orestação. O nosso estudo no Nordeste da Namíbia e Sudoeste da Zâmbia avaliou o potencial dos satélites operacionais de observação da Terra na caracterização dos processos de alteração do uso das terras e na quantifi cação dos seus impactos nas concentraçoes de nutrientes e de carbono orgânico no solo (SOC). Descobrimos que a área de uso agrícola aumentou em 24% entre 2002 e 2013, sobretudo à custa da vegetação natural (i.e. fl oresta). Esta conversão causou um declínio em SOC e N total, havendo uma tencência de aumento do P disponível para plantas nos solos de antigos campos agrícolas. Os efeitos foram mais pronunciados no Nordeste da Namíbia, onde as reservas de SOC totais eram 19,6% (±18.4 SD) mais baixas em terras agrícolas que em fl orestas. Além disso, as perdas de SOC e N total tenderam a resultar no declínio dos rendimentos previstos do milho calculados com o modelo QUEFTS em ~15%, quando comparados com solos de antigos campos agrícolas e fl orestas. No geral, os nossos resultados indicam que a continuação a longo prazo da agricultura arável de subsistência pode reduzir a fertilidade do solo.

Suggested citation:
de Blécourt, M., Röder, A., Gröngröft, A., Baumann, S., Frantz, D. & Eschenbach, A. (2018) Deforestation for agricultural expansion in SW Zambia and NE Namibia and the impacts on soil fertility, soil organic carbon- and nutrient levels In: Climate change and adaptive land management in southern Africa – assessments, changes, challenges, and solutions (ed. by Revermann, R., Krewenka, K.M., Schmiedel, U., Olwoch, J.M., Helmschrot, J. & Jürgens, N.), pp. 242-250, Biodiversity & Ecology, 6, Klaus Hess Publishers, Göttingen & Windhoek. doi:10.7809/b-e.00330