Invasive species in east Africa: current status for informed policy decisions and management

Invasive alien species are the second leading cause of biodiversity loss in the world today. A number of hypotheses have been advanced to explain the proliferation of invasive species. These hypotheses include deficiency of natural enemies in the introduced range, increased competitive ability, increased resource availability and emergence of more vigorous genotypes in the introduced range. In East Africa policy gaps that range from lack of information on invasive species management to how the available information is managed exist. Major gaps include, a deficiency in the number and interest of scientists studying invasion species biology, which subsequently leads to lack of interest in the learning institutions, severe deficiency in predictive and monitoring capacity, lack of coordinated control measures, and poor preparation in government departments. This report serves to identify the major gaps and provide information to assist in the prioritization and optimization of invasive species control and management. It recommends a need for scholars and institutions to develop curricula and recruit more scientists in this discipline. It also recommends an integrative approach, regional coordination and collaboration including sharing of information in an easy and practical language. The review further encourages the government and development agencies at the national and the local level to provide funding and incentives for low and localized programs to slow the spread of existing invasive species in order to protect the yet uninvaded ecosystems. The adaptation of these recommendations will result to control strategies and policy framework based on sound empirical information. It is expected that the report will be valuable for land, environmental managers and other stakeholders.Key words: Invasive species, East Africa, policy, managemen

Properties of Prosopis juliflora and its potential uses in Asal areas of Kenya

A study was done to determine the potential for processing and using Prosopis juliflora for commercial purpose. The effects of the plant on the soil were evaluated as a measure of determining its influence on the environment. Preliminary analysis of three soils samples per site where showed that the highly infested areas had higher moisture content of 10.5+1.35% and was significantly different at 5% level. The pH value of 8.7+1.03 was slightly lower compared to the low infested areas and was not significantly different at 5% level. However, both soils had almost the same bulk density and ECE of 1.1 g/cm3 and 0.03 dm/S respectively. The soil calcium content of 0.88+0.009 mg/l in the high density area was significant low at 5% level whereas the organic carbon content of 1.13+0.027% was significantly high. No significant difference was observed for the magnesium, sodium, potassium, organic matter and phosphorus content at 5% l. Plant samples of Prosopis juliflora were also tested for their nutritive values, especially the leaves, pods, bark and roots. Preliminary results showed that the leaves contain the highest amount of calcium of 6.38+0.248%. However, the leaves are not consumed green by the animals indicating high toxicity. The pods, bark and roots were also found to contain significant proportions of calcium at 5% level. The different parts of the plant had relatively lower phosphorus content of less than 0.25%. Magnesium was higher in the bark at about 3.5% whereas potassium was higher in the pods at about 2%. Nitrogen was higher in the leaves at about 2.5% indicating the suitability of the plant leaves as a nitrogen fixer in the soil. The tissues also showed very high content of vitamin C especially in the green pods (46.3+5.18 m/100g). Thus the pods, leaves and bark can be used as natural sources of vitamin C. The high ash content of 8.9+1.19% in the bark was significantly different at 5% level when compared to the content of the leaves but not other plant parts. This showed high roughage in the plant parts. The nutritive value of the pods showed their high potential for development of nutritive products including juice, wine, gum, powder, essential oils and beverages. The yield for aloe roots as fermenting agent was about 7.1% on 9th day in Prosopis extract having sugar media, 6.3% for yeast, Prosopis extract and honey on the sixth day and 6.1% for extract, sugar and baobab on the sixth day.Key words: Prosopis juliflora, properties, analysis, potential use

Widespread colonisation of Tanzanian catchments by introduced Oreochromis tilapia fishes: the legacy from decades of deliberate introduction

From the 1950s onwards, programmes to promote aquaculture and improve capture fisheries in East Africa have relied heavily on the promise held by introduced species. In Tanzania these introductions have been poorly documented. Here we report the findings of surveys of inland water bodies across Tanzania between 2011 and 2017 that clarify distributions of tilapiine cichlids of the genus Oreochromis. We identified Oreochromis from 123 sampling locations, including 14 taxa restricted to their native range and three species that have established populations beyond their native range. Of these three species, the only exotic species found was blue-spotted tilapia (Oreochromis leucostictus), while Nile tilapia (Oreochromis niloticus) and Singida tilapia (Oreochromis esculentus), which are both naturally found within the country of Tanzania, have been translocated beyond their native range. Using our records, we developed models of suitable habitat for the introduced species based on recent (1960–1990) and projected (2050, 2070) East African climate. These models indicated that presence of suitable habitat for these introduced species will persist and potentially expand across the region. The clarification of distributions provided here can help inform the monitoring and management of biodiversity, and inform policy related to the future role of introduced species in fisheries and aquaculture