Urban afforestation in Tanzania: Lessons from Sokoine University of Agriculture landscape inventory

Abstract

A study to ascertain the extent to which tree-planting in urban areas of Tanzania have been adhering to the prescribed standards essential for provision of the anticipated services was carried out by taking Sokoine University of Agriculture main campus landscape as a case study. Data pertaining to species and genera composition, age distribution, and overall heath status were collected through a survey which involved 100% sampling intensity. All trees and shrubs encountered were identified by their botanical names, along with taking measurements on their appropriate location, tree-size, and overall health status. The study revealed a tendency of concentrating on few plant species, while much other potential were available. While the acceptable standard requires species not to exceed 10 %, some species were represented by more than 24 %. Diversification at genera level ideal as none of the genera exceeded the prescribed standard of 30%. The distribution of plants in terms of age class was not ideal as the observed proportion in the young (283%), mature (62.7%), and over mature (9.0) diverged significantly from the respective prescribed standards of 20%, 60%, and 20%. The overall health status of trees was good, with this class representing more than 95% of the total trees observed. Excessive concentration of few species and genera has a disadvantage, particularly in the incidences of pest and disease outbreak. Large areas could be left bare if a species happened to be severely attacked, which in turn reduces the overall beauty of a landscape. Inappropriate age class distribution complicate future landscape maintenance since many trees may have to be removed and replanted at once. This tends to increase the cost of maintenance, and may make replacement exercise impossible. It is concluded that urban afforestation in most towns of Tanzania are likely to have not adhered to the prescribed standards, as policies related to tree planting have been similar in most cities. It is recommended that cities and urban authorities should consider the use of landscape experts in deciding the appropriate ways of handling urban forest, so as to maximize the benefits that could accrue.