The aim of this thesis was to investigate vegetation management within the agricultural landscape and determine at which scale and which practices are most beneficial to invertebrate... Show moreThe aim of this thesis was to investigate vegetation management within the agricultural landscape and determine at which scale and which practices are most beneficial to invertebrate assemblages and the associated food web. We determined invertebrate abundance, species richness, and diversity using sticky boards, sweep netting, and pitfall traps to sample. Our examination ranged from the field level to the landscape level of 6000 m. Practices examined include mowing, prairie restoration, and summer fire. Management recommendations are made based on the results of our research. Show less
Metals in soils can pose a serious threat to soil dwelling organisms, plants, and human beings. A major uncertainty in terrestrial ecological risk assessment for metals is theintegrated effect of... Show moreMetals in soils can pose a serious threat to soil dwelling organisms, plants, and human beings. A major uncertainty in terrestrial ecological risk assessment for metals is theintegrated effect of the physicochemical properties of soil on toxicity and how this allows for extrapolation of toxicity data across soils. The recognition that soil type is an important factor that determines metal toxicity, goes along with the increasing insight into bioavailability. There is a growing consensus that only a proportion of the total amount of metal in soil isavailable for uptake by organisms and subsequently induces toxic effects. Development of mechanistically underpinned approaches for explaining and predicting availability effects onmetal toxicity has been the subject of many research efforts in terrestrial ecotoxicology. Show less
Population growth and the drop in the returns from the major cash crop (coffee) for small farmers are the main drivers that have influenced the farming systems and mobility of farmers in the... Show morePopulation growth and the drop in the returns from the major cash crop (coffee) for small farmers are the main drivers that have influenced the farming systems and mobility of farmers in the Western Highlands of Cameroon (WHC). The main objective of this research activity was to determine the interactions between farming systems and human mobility in the WHC. A comparative study was conducted through household and field surveys in three villages and conceptualized based on the systems approach. The different types of mobility were influenced by household social factors, the quest for ‘high valued' farm plots and hired labour. Urban-rural migration contributed to occupation diversification and social mobility. The sustainability factor was a function of land use intensity, intensity of off-farm inputs, the household adjustment factor and mobility of the household. The sacred groves were rich in plant diversity of varied ecological and economic importance. Nitrogen mining was common at all levels of the farming system. These determinants and types of mobility claims are pertinent to the research area; the sustainability results of the farming systems reflect the reality on the ground; the nutrient flux evaluated at the crop and farm levels constitute a valuable database for future research. Show less
Most scientific literature on hyena-human interrelationships in Africa sug-gests conflict situations, often resulting in the killing of hyenas. Hyenas survive with difficulty in human-altered... Show moreMost scientific literature on hyena-human interrelationships in Africa sug-gests conflict situations, often resulting in the killing of hyenas. Hyenas survive with difficulty in human-altered habitats and coexistence between hyenas and local communities is problematic. This is because hyenas need extensive areas, usually with few people and sufficient prey. In contrast to this, the present dissertation presents an exceptional case of peaceful co-existence between hyenas and humans. Based on regular observations of hyenas and anecdotal reports, I hypothesized that hyenas in the Tigray re-gion, northern Ethiopia, survive in human-dominated landscapes because of a unique combination of adaptation to anthropogenic food and cultural tolerance towards hyenas. My research aimed to investigate hyena ecology and behavior in human-dominated and prey-depleted landscapes in Tigray. Hyenas are common in many parts of Ethiopia, and in most of those areas, prey populations have been depleted. In northern Ethiopia, the natural prey base is depleted due to agricultural expansion, deforestation, human settle-ment, and habitat fragmentation and degradation Show less
To seek answers to the issues on GM corn adoption in the Philippines, the thesis focused to find answers on the general question: How can genetically modified (GM) corn and its attributed changes... Show moreTo seek answers to the issues on GM corn adoption in the Philippines, the thesis focused to find answers on the general question: How can genetically modified (GM) corn and its attributed changes in agricultural practices affect the agro-ecosystem's biodiversity and the economic status and social life of the farmers? Survey of Asian corn borer (ACB) in Chapter2 showed that Bt corn efficiently reduce borer pest problem and damage to plants by 44%. No secondary pest outbreak was found in Bt cornfields yet, occurrence of ACB though at an insignificant level, could imply potential development of Bt toxin resistance. On biodiversity (Chapters3 and 4), the total invertebrate abundance, surface dwellers and soil dwellers were significantly higher in non-GM cornfields than in Bt and BtHT cornfields. Insecticide-sprayed non-GM cornfields harbored more invertebrates than unsprayed Bt or BtHT cornfield. Surveyed cornfields with a minimum of two years cultivation of GM corn manifested that non-Bt cornfields had significantly higher abundance and species richness of non-target invertebrates than the Bt and BtHT fields. On economic aspect (Chapter5), the non-GM corn was not statistically different from Bt, BtHT and HT corn in terms of production output(PO), net income(NI), production-cost ratio(M) and return on investments(ROI). Results of econometric and Blinder-Oaxaca analyses demonstrate that at present GM corn hybrids do not explicitly manifest economic advantage compared to non-GM corn. On social aspect (Chapter6), GM corn adoption proved to be influenced by the perceived economic advantage, extent of knowledge, level of satisfaction and extent of first-hand experience. The foremost reason for not adopting GM corn was the cost of seed. Herbicide-tolerant (HT) corn, Bacillus thuringiensis (Bt) corn, BtHT corn, abundance, species richness, Asian corn borer, secondary pest, genetically modified (GM) corn, non-GM corn, farm economics, decomposition analysis Show less
The aim of this thesis was to investigate long term population dynamic processes in Black-tailed Godwit populations resulting from habitat fragmentation on three different spatial scales by using... Show moreThe aim of this thesis was to investigate long term population dynamic processes in Black-tailed Godwit populations resulting from habitat fragmentation on three different spatial scales by using genetics. We demonstrated that egg shell membranes provide a good alternative DNA source for population genetic studies compared to blood samples. Through the usage of egg shell membranes we could conduct the genetic studies in this thesis a large spatial scales. Genetic population structuring was studied here because Black-tailed Godwit breeding areas seemed geographically fragmented and it was unclear if this had led to genetic separation and inbreeding as well. On a local scale we did not detect any genetic populations structuring as an effect of habitat fragmentation. We showed that habitat fragmentation, although geographically visible, has not yet lead to genetic differences between Dutch breeding populations. As such it seems that Dutch breeding areas of the Black-tailed Godwit consist of a single panmictic population. On a global scale this thesis confirmed the presence of three genetically distinct groups now recognized as subspecies. However, no clear genetic differences were found between L. l. limosa across most of its current breeding range. Possibly, there is some genetic differentiation between L. l. limosa breeding areas in the Netherlands and Sweden. Show less
Raptors in West Africa’s savannas have strongly declined the past four decades and many species now survive only in a few pockets of intact habitat, mostly inside protected areas, while some... Show moreRaptors in West Africa’s savannas have strongly declined the past four decades and many species now survive only in a few pockets of intact habitat, mostly inside protected areas, while some species are on the brink of extinction. Little is known about the processes that sustain raptor populations within increasingly human-transformed savanna landscapes, and clues to the mechanisms and causal drivers behind population declines remain little studied. Moreover, it is unclear how changing conditions differently affect the diverse assemblage of Afrotropical and Palearctic raptors, which depend on the West Africa’s savannas for part or most of their life cycle, and how vulnerability, or adaptability to changing environments, relate to life-history traits such as their mobility, sex, age, body mass, and diet. This thesis quantifies the effects of land transformation on distribution, foraging, diet, and reproductive output of Palearctic and Afrotropical raptors, both migratory and sedentary, in West African savannas, to increase the knowledge that can support conservation efforts directed at the persistence of rich raptor populations in this part of the world. Show less
Lions in Waza National Park Cameroon were studied with focus on lion ecology and the human-lion conflicts due to livestock predation. The number of adult lions has declined from 40-60 in 2002 to 14... Show moreLions in Waza National Park Cameroon were studied with focus on lion ecology and the human-lion conflicts due to livestock predation. The number of adult lions has declined from 40-60 in 2002 to 14-21 in 2008, which represents a reduction of about 65% in 6 years. The human-livestock pressure on the park is enormous, 31% of photographs captured by camera traps in 2008, were of humans and livestock in the park. Retaliatory killing of lions by herders is high, as lions increasingly predate on cattle due to the strong decline of their natural prey. Lion home ranges have increased from a mean of 630 km² in 2000 to 1015 km² in 2008, extending to areas outside the park. Livestock constitutes as much as 21.6% of the diet. Characteristics of the diet and movements of the lion reflect a survival strategy of lions under highly disturbed conditions. Although the Waza lion population now seems to be most threatened, concerte d conservation efforts could save this population from local extinction. The government must greatly improve park protection through the park management authority and law enforcement, as well as providing financial and human resources for the park. Furthermore, local communities living close to the park must receive direct benefits from park revenues Show less
The research focused on two main objectives: (1) understanding the processes behind the spatial and temporal patterns of plant diversity on ditch banks; (2) identifying options for the conservation... Show moreThe research focused on two main objectives: (1) understanding the processes behind the spatial and temporal patterns of plant diversity on ditch banks; (2) identifying options for the conservation and restoration of plant species diversity on ditch banks. The spatial and temporal variation of plant diversity have been explained primarily on the basis of dispersal processes, which imply that conservation management should focus on facilitating dispersal between sites. Nature reserves can act as a source of seeds for the surrounding areas, the presence of nature reserves, therefore, should be given greater consideration in management policies. In view of the large areas of agricultural lands in the Netherlands, these areas can contribute considerably to the country’s overall plant diversity. Agri-environmental schemes (AES) should therefore consider large-scale contributions to diversity instead of focus entirely on the farm scales. We suggest that farmers implementing AES would be more successful if they selected ditch banks adjacent to those where a similar management regime is already in force. Show less
SMALL Savannah is an Environmental Information System designed for the integrated analysis and sustainable land management in the savannas region of the Far North of Cameroon. This system combines... Show moreSMALL Savannah is an Environmental Information System designed for the integrated analysis and sustainable land management in the savannas region of the Far North of Cameroon. This system combines an observation and spatial analysis module for the representation of phenomena from various geographic data sources, with a module for the explanation and prediction of land use pattern and changes, and a dynamic modelling and simulation module for the exploration of possible land use change trajectories. Due to a high demographic pressure combined with an increasing human mobility, many changes have occurred in the land use of the study area during the last two decades. These dynamics have led to land saturation resulting in more competition between land uses and conflicts between actors. The spatial and quantitative analysis for the observation period (1987-1999) indicates that accessibility to the main urban centre, soil suitability and population pressure, have been the main driving factors behind this process. According to assumption formulated for future development, it is expected that changes in land use of this area will continue to depend on these factors. But, the land use trajectories will be mainly influenced by the implication of urban actors and the potential investment of local actors for improving land quality and management. The simulations performed for the period 1999 to 2010 indicate areas where changes are likely to occur, thus providing a possibility to evaluate the spatial impact of a given land management policy. The information system under development is an appropriate tool for a regional monitoring system of land use change and rural development. It can be used by scientist and actors involved in land use planning for decision making and adaptive land use management. Another utilisation can be considered with local actors in order to discuss and prepare any concertation or negotiation when dealing with participatory approach of land use and management. Show less
Africa is often called ‘the fire continent’ based on the high frequency and large extent of burning. Over 200 million hectares of land are regularly burned, mostly savanna areas. In this thesis the... Show moreAfrica is often called ‘the fire continent’ based on the high frequency and large extent of burning. Over 200 million hectares of land are regularly burned, mostly savanna areas. In this thesis the ecological effects of fire on savanna herbivores in Bénoué National Park in North Cameroon are described. Analyses of grass quality show that unburned grass swards are of insufficient quality to sustain grazing herbivores during the dry season. Post-fire regrowth, however, is of much better quality, as it contains higher nutrient levels and higher digestibility. As a result, herbivores strongly prefer to graze on burned swards. This is more than just a simple food preference: most grazers probably would not survive the dry season on unburned swards. Because of this, fire proves to be a major factor governing diversity patterns of herbivores, both at the local scale (the park) and at larger scales (West Africa as a whole). In this thesis it is argued that the species richness of grazing herbivores throughout West Africa is primarily governed by fire, rather than by moisture or soil fertility. Without fire it would thus be impossible to maintain current diversity levels of herbivores in the Guinea savanna zone of West Africa. Show less
This investigation is an attempt to gain a better understanding of the religious and socio-political organization of pre-colonial Tobabatak society. In literature the traditionally stateless... Show moreThis investigation is an attempt to gain a better understanding of the religious and socio-political organization of pre-colonial Tobabatak society. In literature the traditionally stateless Tobabatak society is usually depicted as being organized principally along kinship lines and there is still a widespread perception that in pre-colonial times there were no more highly developed political units than villages. Fieldwork, archival research, and research into old Tobabatak texts have produced a different picture. Tobabatak society did indeed never transform into statehood (in the sense of having a centralized government with the military power to enforce its decisions) but it had a functional alternative at its disposal: The many genuinely democratically organized ‘house-organizations’ (bius) of which the society consisted, each composed of thousands or even tens of thousands of members, were abl e to organize co-operation for the construction of irrigation-facilities and other communal projects (sometimes on a huge scale) and for the permanent infrastructure of hydraulic agriculture. Within these house-organizations the parbaringin as spiritual as well as political representatives of the smaller units of society on the higher levels, and the paniaran as the representatives of the women played a leading role without ever using any military might. Show less
Everybody still knows the images of hunger and drought in the dry zones of Africa (the Sahel). These last years the situation for the millions of people living there has stabilised due to the fact... Show moreEverybody still knows the images of hunger and drought in the dry zones of Africa (the Sahel). These last years the situation for the millions of people living there has stabilised due to the fact that rainfall has not failed. But what about the future? The population is still growing rapidly, and industries to absorb these numbers does not exist. The future of the Sahel depends on the investments of the farmers to improve the productivity of their arable land. But the people are poor, there are no good markets to trade new agricultural products, and there is still some bushland available where new fields may be made if the old fields are exhausted. The dissertation deals with this bushland in the Sahel. In the bush, we find trees, grass and bushes, which are used for cattle, wood supply, medicines and may other functions, such as fallow and hunting. Is it possible to estimate the value of this land? Will all of this bushland be lost in the near future, converted to arable land to feed the ever higher population? After studying these questions in a specific area in Cameroon, Wassouni concludes that it is unwise to wait till all bushland is used up. Active protection of the bush, by the government but also by local people, is necessary to stimulate the farmers to invest in their land before they have become so poor that they no longer can. Show less
De biodiversiteit op akkerbouwbedrijven staat nog steeds sterk onder druk. Het toevoegen van criteria voor natuur aan keurmerken voor de landbouw zou mogelijkheden kunnen bieden om de... Show moreDe biodiversiteit op akkerbouwbedrijven staat nog steeds sterk onder druk. Het toevoegen van criteria voor natuur aan keurmerken voor de landbouw zou mogelijkheden kunnen bieden om de biodiversiteit in het landelijk gebied te kunnen verbeteren. Tot nu toe wordt er echter nog weinig aandacht aan natuur besteed in bestaande keurmerken voor akkerbouwproducten en -bedrijven. Naar aanleiding hiervan zijn een aantal indicatoren voor natuur op akkerbouwbedrijven ontwikkeld. Deze indicatoren richten zich op de oppervlakte natuur per bedrijf, de plantensoortenrijkdom van slootkanten en de schuilplaatsgelegenheid voor vogels en kleine zoogdieren.De toepassing van deze indicatoren liet zien dat de ontwikkelde methoden geschikt zijn voor het vaststellen van verschillen in soortenrijkdom naar aanleiding van verschillen in beheer, landbouwpraktijk en regio’s onafhankelijk van de grootte van het landbouwbedrijf. Op basis van de gevonden resultaten zijn de volgende natuurbeheer criteria voorgesteld voor opname in een bedrijfskeurmerk voor akkerbouwbedrijven: 1) 5% landschapselementen per landbouwbedrijf; 2) bufferzones langs alle landschapselementen afhankelijk van de methode van bemesten en spuiten; 3) ecologisch beheer (maaien en afvoeren) van slootkanten gebufferd met een akkerrand; 4) aanleg van akkerranden en een gevarieerd slootkantbeheer.Daarnaast kunnen de ontwikkelde indicatoren gebruikt worden om de natuurresultaten te volgen en te beoordelen of de boer voldoet aan de gestelde eisen van het keurmerk. Show less
