Status, Impact and Management of Invasive Alien Species in Tanzania

Invasive alien species (IAS) are among the significant drivers of environmental change worldwide and important causes of biodiversity losses. They contribute to economic hardship and social instability, placing constraints on sustainable development, economic growth, and ecological problems in various parts of the world, including Tanzania. This study was undertaken to provide information on the status of invasive species and their management needs in Tanzania. The study used three methodological approaches including documentary search, interviews with relevant stakeholders and limited field visits. Findings from the study have indicated that the awareness, trends, distribution and impacts of the invasive alien species in Tanzania are variable, and similarly are the management and control requirements and practices for these species. Among the major impacts associated with the IAS in the country include loss of biodiversity, where in some cases has caused disappearance of certain species of fauna and flora, social and economic distress to human being due to the disappearance of plants and animal species that are regarded as important sources of livelihoods. The study shows that currently there is limited demonstrated capacity in terms of human and financial resources to address the issue of IAS, except for a few cases such as the water hyacinth (Eichhornia crassipes) in Lake Victoria. In addition, there are no clearly defined long term strategies to address the issue of invasive species in many institutions. Experience shows that many of the legislations and policies dealing with biodiversity and/or resource management in the country do not directly address invasive alien species. This shortfall may be responsible for the inadequate attention being accorded to the management of invasive species. Thus for effective management of invasive alien species, policies and legislations should be encouraged to directly deal with invasive species. Such situation calls for integrated efforts including various institutional frameworks and collaborations.Key words: Invasive alien species, biodiversity loss, management of IAS,sustainable development, Tanzania

Determinants of woody encroachment and cover in African savannas

Savanna ecosystems are an integral part of the African landscape and sustain the livelihoods of millions of people. Woody encroachment in savannas is a widespread phenomenon but its causes are widely debated. We review the extensive literature on woody encroachment to help improve understanding of the possible causes and to highlight where and how future scientific efforts to fully understand these causes should be focused. Rainfall is the most important determinant of maximum woody cover across Africa, but fire and herbivory interact to reduce woody cover below the maximum at many locations. We postulate that woody encroachment is most likely driven by CO2 enrichment and propose a two-system conceptual framework, whereby mechanisms of woody encroachment differ depending on whether the savanna is a wet or dry system. In dry savannas, the increased water-use efficiency in plants relaxes precipitation-driven constraints and increases woody growth. In wet savannas, the increase of carbon allocation to tree roots results in faster recovery rates after disturbance and a greater likelihood of reaching sexual maturity. Our proposed framework can be tested using a mixture of experimental and earth observational techniques. At a local level, changes in precipitation, burning regimes or herbivory could be driving woody encroachment, but are unlikely to be the explanation of this continent-wide phenomenon

Climate change effects on people’s livelihood

Generally climate is defined as the long-term average weather conditions of a particular place, region, or the world. Key climate variables include surface conditions such as temperature, precipitation, and wind. The Intergovernmental Panel on Climate Change (IPCC) broadly defined climate change as any change in the state of climate which persists for extended periods, usually for decades or longer (Allwood et al. 2014). Climate change may occur due to nature’s both internal and external processes. External process involves anthropogenic emission of greenhouse gases to the atmosphere, and volcanic eruptions. The United Nations Framework Convention on Climate Change (UNFCCC) made a distinction between climate change attributable to human contribution to atmospheric composition and natural climate variability. In its Article 1, the UNFCCC defines climate change as “a change of climate which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time periods” (United Nations 1992, p. 7)

Agricultural Commercialisation and Its Implications on Agrodiversity Management in the Drylands of Central Tanzania

The study examines the linkages between agricultural commercialisation and agrodiversity management. It considers agricultural commercialisation an important socio-economic aspect with varied environmental implications, particularly in relation to agro-diversity management. The study was undertaken in Kondoa and Kongwa Districts, in the semiarid central Tanzania. The aim of this study was to examine the implications of agricultural commercialization on agro-diversity management, food security and the environment in general. A variety of methods were used in the study including participatory assessments techniques, field visits and household surveys. Household data was analysed using SPSS. The findings from this study indicate that for decades agricultural production in the semiarid areas of central Tanzania has been centred on production of a diverse number of crops though concentrated on sorghum and millets as the most drought tolerant grain crops. However, from the mid-1980s the balance has shifted in favour of cereal crops like maize, which has become among the major cash-earning crop. Other prominent commercial crops included pigeon peas, sunflower and simsim. Commercial crops appear to be expanding at the expense of traditional drought tolerant crops such as bulrush millet and sorghum, thereby influencing the local agro-diversity. The abandonment of some crops e.g. castor oil plants in favour of market crops also appear to affect the agrobiodiversity in the study areas. It has been found that expansion of farms is a major factor for environmental degradation through deforestation, declining soil fertility due to continuous cultivation and emergence of noxious weeds such as Striga. On the other hand agricultural commercialization appears to have been associated with improvement in food security, household income, housing conditions and education for children. However the emphasis of the less drought tolerant crops like maize in these semiarid areas makes the sustainability of the agricultural system very uncertainKeywords: Agricultural commercialisation, agrodiversity, food security, semiarid Tanzani