Land-use changes and the invasion dynamics of shrubs in Baringo (original) (raw)
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Prosopis julifloraInvasion and Rural Livelihoods in the Lake Baringo Area of Kenya
Conservation and Society, 2008
Global concern about deforestation caused by fuelwood shortages prompted the introduction of Prosopis juliflora to many tropical areas in the 1970s and 1980s. P. juliflora is a hardy nitrogen-fixing tree that is now recognised as one of the world's most invasive alien species. The introduction and subsequent invasion of P. juliflora in the Lake Baringo area of Kenya has attracted national media attention and contradictory responses from responsible agencies. This paper presents an assessment of the livelihood effects, costs of control and local perceptions on P. juliflora of rural residents in the Lake Baringo area. Unlike some other parts of the world where it had been introduced, few of the potential benefits of P. juliflora have been captured and very few people realise the net benefits in places where the invasion is most advanced. Strong local support for eradication and replacement appears to be well justified. Sustainable utilisation will require considerable investment and institutional innovation.
Spatial Evolution of Prosopis Invasion and its Effects on LULC and Livelihoods in Baringo, Kenya
Woody alien plant species have been deliberately introduced globally in many arid and semi-arid regions as they can provide services and goods to the rural poor. However, some of these alien trees and shrubs have become invasive over time, with important impacts on biodiversity, ecosystem services and human well-being. Prosopis was introduced in Baringo County, Kenya, in the 1980s, but since then it has spread rapidly from the original plantations to new areas. To assess land use and land cover (LULC) changes and dynamics in Baringo, we used a combination of dry and wet season Landsat satellite data acquired in a 7-year time interval between 1988 and 2016 and performed a supervised Random Forest classification. For each time interval we calculated extent of the invasion, rates of spread and gains and losses of specific LULC classes. We further assessed the relative importance of Prosopis invasion on LULC changes and ultimately on the provision of ecosystem services rural people depe...
The increase in biomass and abundance of woody plant species, often thorny or unpalatable, coupled with the suppression of herbaceous plant cover, is a widely recognized form of rangeland degradation. Bush encroachment therefore has the potential to compromise rural livelihoods in Africa, as many depend on the natural resource base. The causes of bush encroachment are not without debate, but fire, herbivory, nutrient availability and rainfall patterns have been shown to be the key determinants of savanna vegetation structure and composition. In this paper, these determinants are discussed, with particular reference to arid and semi-arid environments of Africa. To improve our current understanding of causes of bush encroachment, an integrated approach, involving ecological and indigenous knowledge systems, is proposed. Only through our knowledge of causes of bush encroachment, both direct and indirect, can better livelihood adjustments be made, or control measures and restoration of savanna ecosystem functioning be realized.
Prosopis juliflora Invasion and Rural Livelihoods in the Lake Baringo Area of Kenya
Conservation and Society, 2008
Global concern about deforestation caused by fuelwood shortages prompted the introduction of Prosopis juliflora to many tropical areas in the 1970s and 1980s. P. juliflora is a hardy nitrogen-fixing tree that is now recognised as one of the world's most invasive alien species. The introduction and subsequent invasion of P. juliflora in the Lake Baringo area of Kenya has attracted national media attention and contradictory responses from responsible agencies. This paper presents an assessment of the livelihood effects, costs of control and local perceptions on P. juliflora of rural residents in the Lake Baringo area. Unlike some other parts of the world where it had been introduced, few of the potential benefits of P. juliflora have been captured and very few people realise the net benefits in places where the invasion is most advanced. Strong local support for eradication and replacement appears to be well justified. Sustainable utilisation will require considerable investment and institutional innovation.
African Journal of Ecology, 2009
Invasive plants have invaded swathes of grasslands in Lake Nakuru National Park thus necessitating the Park management to institute measures to control them. Despite this, information on the status and impact of invasive plants in these grasslands is lacking. Six grassland types were identified and assigned random numbers. Five study sites were then randomly selected from each grassland type. The Point-Centre Quarter method was used to determine the distribution and density of seven major invasive plants, whilst their impact was assessed by comparing biomass and crude protein content of important forage grasses in invaded and noninvaded grasslands. Results show that the distribution of invasive plants did not differ among the grasslands (F5, 30 = 1.47, P = 0.229) but their densities differed among the plants (F6, 30 = 20.99, P < 0.001). The mean biomass in invaded and noninvaded grasslands (22 g m−2 versus 37.2 g m−2) was significantly different (t-test, P < 0.05), while crude protein content of grasses in invaded (7.73, % DM) and noninvaded (9.3, % DM) patches was not significantly different (t-test; P > 0.05). Our results suggest that invasive plants lower grass production and hence might reduce food availability to grazers.Des plantes invasives ont envahi des étendues de prairies du Parc National du Lac Nakuru, ce qui oblige la gestion du parc à instaurer des mesures pour les contrôler. Malgré cela, on manque toujours d’informations sur le statut et l’impact des plantes invasives sur ces prairies. On a identifié six types de prairies et on leur a attribué un numéro au hasard. On a ensuite choisi au hasard cinq sites d’étude pour chaque type. La méthode des quartiers par point centré fut utilisée pour déterminer la distribution et la densité de sept plantes invasives importantes, tandis que l’on évaluait leur impact en comparant la biomasse et le contenu en protéine brute des herbes fourragères importantes dans les prairies envahies et non envahies. Les résultats montrent que la distribution des plantes invasives ne différait pas selon les prairies (F 5,30 = 1,47, P = 0,229), mais que leur densité différait parmi les plantes (F6, 30 = 20.99, P < 0.001). La biomasse moyenne dans les prairies envahies et non envahies (22 g m−2 versus 37.2 g m−2) était significativement différente (test de t : P < 0,05) alors que le contenu en protéine brute dans les îlots de prairies envahies (7,73, % DM) et non envahies (9,3, % DM) n’était pas significativement différent (Test de t: P > 0,05). Nos résultats suggèrent que les plantes invasives diminuent la production herbeuse et pourraient donc réduire la disponibilité de nourriture pour les animaux qui broutent.
Ecological impacts of Prosopis invasion in Riverine forests of Kenya
2012
Prosopis chilensis, Prosopis juliflora and Prosopis pallida were widely introduced in tropical drylands, where they have become naturalized and invasive. Invasion management is partially hampered by species misidentification because of morphological similarities between species and between species and their hybrids. In Kenya, species identification is even more challenging as several species were introduced within sites. Since biological invasions are invoked by either the susceptibility of a habitat to invasion (invasibility) or the invasive traits of a species (invasiveness), proper knowledge of these two factors is required for proper invasion management. In this dissertation, we used field, greenhouse and laboratory studies to: 1) evaluate invasibility of Turkwel riverine forest, and 2) invasiveness of Prosopis species by determining: 2) ecological impacts of Prosopis invasion, 3) underlying mechanisms for observed ecological impacts and 4) species composition and genetic diversity of Prosopis populations in Kenya. Invasibility was evaluated by comparing Prosopis occurrence between undisturbed invasion resistant forests with invasion susceptible forest gaps; ecological impacts of Prosopis invasion determined by comparing herbaceous species and tree regeneration among Acacia tortilis, Prosopis and a mixture of A. tortilis and Prosopis species canopies; underlying mechanisms of observed ecological impacts determined by assessing the impact of A. tortilis and Prosopis litter on A. tortilis and Prosopis species seed germination and seedling growth; and species composition and genetic diversity of Kenyan Prosopis populations determined by comparing Kenyan populations at Bamburi, Bura, Isiolo, Marigat, Taveta and Turkwel with P. chilensis, P. juliflora and P. pallida references for relatedness and genetic diversity. We found that both the forest and the forest gaps were equally susceptible to Prosopis invasion, suggesting that invasion was spontaneous and independent of the assumed habitat invasibility variation. The ecological impact study revealed reduction of ground vegetation cover, herbaceous species diversity and termination of A. tortilis regeneration by Prosopis. Termination of A. tortilis regeneration may be attributed to strong reduction of A. tortilis and Prosopis species seed germination by increasing Prosopis litter concentration in the viii soil in greenhouse studies. Relatedness studies between the Kenya Prosopis populations and the reference species revealed the clustering of P. chilensis with Taveta population, P. juliflora with Bura, Marigat and Isiolo and P. pallida with Bamburi. Results suggested that Turkwel population was a likely hybrid between P. chilensis and P. juliflora. Genetic diversity of populations at Bamburi, Isiolo and Marigat was higher than that of the reference species that they clustered with. Bamburi, Isiolo, Taveta and Turkwel populations revealed genetic uniqueness, as demonstrated by generation of private markers by a specific primer in each of the population. Prosopis juliflora and its hybrid occurred in areas currently classified as most invaded. Based on the results, we concluded that P. juliflora and its hybrid are the most aggressive invaders and that riverine forest invasion was invoked more by species invasiveness and not habitat invasibility. The invasiveness traits found in our study were: 1) Allelopathy of Prosopis litter which reduces herbaceous species ground vegetation cover and herbaceous species diversity; and inhibited regeneration of A. tortilis. 2) Unique site adaptations of introduced germplasm evident from the genetic differentiation of introduced germplasm depending on site, and 3) hybridization that was evident from a P. chilensis-P. juliflora hybrid in Turkwel.
Pollen, People and Place: Multidisciplinary Perspectives on Ecosystem Change at Amboseli, Kenya
Frontiers in Earth Science, 2018
This study presents a multidisciplinary perspective for understanding environmental change and emerging socio-ecological interactions across the Amboseli region of southwestern Kenya. We focus on late Holocene (<5,000 cal yr. BP) changes and continuities reconstructed from sedimentary, archeological, historical records and socio-ecological models. We utilize multidisciplinary approaches to understand environmental-ecosystem-social interactions over the longue durée and use this to simulate different land use scenarios supporting conservation and sustainable livelihoods using a socio-ecological model. Today the semi-arid Amboseli landscape supports a large livestock and wildlife population, sustained by a wide variety of plants and extensive rangelands regulated by seasonal rainfall and human activity. Our data provide insight into how large-scale and long-term interactions of climate, people, livestock, wildlife and external connections have shaped the ecosystems across the Amboseli landscape. Environmental conditions were dry between ∼5,000 and 2,000 cal yr. BP, followed by two wet periods at ∼2,100-1,500 and 1,400-800 cal yr. BP with short dry periods; the most recent centuries were characterized by variable climate with alternative dry and wet phases with high spatial heterogeneity. Most evident in paleo and historical records is the changing woody to grass cover ratio, driven by changes in climate and fire regimes entwined with fluctuating elephant, cattle and wild ungulate populations moderated by human activity, including elephant ivory trade intensification. Archeological perspectives on the occupation of different groups (hunter-gatherers, pastoralists, and farmers) in Amboseli region and the relationships between them are discussed. An overview of the known history of humans and elephants, expanding networks of trade, and the arrival and integration of metallurgy, livestock and domesticated crops in the wider region is provided. In recent decades, increased runoff and flooding have resulted in the expansion of wetlands and a reduction of woody vegetation, compounding problems created by increased enclosure and privatization of these landscapes. However, most Githumbi et al. Long-Term Multidisciplinary Perspectives at Amboseli, Kenya of the wetlands outside of the protected area are drying up because of the intensified water extraction by the communities surrounding the National Park and on the adjacent mountains areas, who have increased in numbers, become sedentary and diversified land use around the wetlands.