Indigenous versus exotic tree species used in silviculture and agroforestry: An overview from Burundi Seed Centre data

Abstract

In Burundi, natural ecosystems are found mainly in protected areas and indigenous species seem to be scarce in silvicultural and agroforestry programs. The indisputable enthusiasm of the population to use Eucalyptus has already completely transformed the Burundian landscape. The present study aims at analyzing the extent of the exotic species use versus indigenous by different stakeholders, among them the Government of Burundi. Sales statistics (2012-2021) from the Burundian Office for the Protection of the Environment seed bank were analyzed. The study reveals that out of 23 species, seeds of only three indigenous tree species are sold. The latter corresponds to 27% of the total seed weight, representing only 0.11% of the total seed number. Eucalyptus div. sp. are the most dedicated to silvicultural programs with 99.63% of total seeds; no indigenous tree species is known for silviculture in Burundi. Concerning agroferestry, indigenous species are represented by Maesopsis emenii, Markhamia lutea and Polycias fulva totaling 29.03 % of total seed weight, equivalent to only 1.17 % of the total seed number. The most used species are exotic, namely Grevillea robusta, Calliandra calothyrsus and Cedrella serrulata, representing 57%, 25.43% and 11.36% of total seed number respectively. Likewise, the Government programs as well as other stakeholders are choosing seed species in the same way. This study showed the exclusive use of exotic species in silvicultural where Eucalyptus div.sp. have won over foresters and the general population due to their rapid growth, high productivity and regeneration regardless soil quality. The present study confirms the quasi-exclusive use of exotic tree species in silvicultural and agroforestry programs by different actors. Our findings suggest the need to seek for alternative indigenous tree species to promote. Relevant policies should be revised and implemented accordingly for the soil conservation and ecosystem restoration as well as reforestation.