Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    We will mail you new results for this query: keywords==Abundance
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Camera trapping reveals trends in forest duiker populations in African National Parks
O'Brien, Timothy G. ; Ahumada, Jorge ; Akampurila, Emmanuel ; Beaudrot, Lydia ; Boekee, Kelly ; Brncic, Terry ; Hickey, Jena ; Jansen, Patrick A. ; Kayijamahe, Charles ; Moore, Jennifer ; Mugerwa, Badru ; Mulindahabi, Felix ; Ndoundou-Hockemba, Mireille ; Niyigaba, Protais ; Nyiratuza, Madeleine ; Opepa, Cisquet K. ; Rovero, Francesco ; Uzabaho, Eustrate ; Strindberg, Samantha - \ 2019
Remote Sensing in Ecology and Conservation (2019). - ISSN 2056-3485
Abundance - Africa - bushmeat - camera trapping - Forest duikers - occupancy - protected areas - Royle-Nichols models

Bushmeat hunting is widely cited as cause for declines of wildlife populations throughout Africa. Forest duikers (Bovidae, Cephalophinae) are among the most exploited species. Whether current harvest rates imperil duikers is debated because of the difficulty of accurately assessing population trends. To assess population trends, we first reviewed literature for historical duiker population estimates. Second, we used systematic camera-trap monitoring to assess population trends for 15 populations of nine duiker species in six national parks in Central and East Africa. We analysed annual monitoring data using Royle-Nichols heterogeneity-induced occupancy models to estimate abundance/sample point and derive occupancy estimates. Published density estimates indicate that duiker populations declined significantly throughout Africa between 1973 and 2013. There was a wide range of densities depending on species ((Formula presented.) range: 0.26–20.6 km−1) and whether populations were hunted ((Formula presented.) =6.3 km−1) or unhunted ((Formula presented.) = 16.3 km−1). More recent analysis of camera-trap monitoring produced different results. Estimated mean point abundance over time was between 0 and 0.99 individuals/point for four populations, between 1.0 and 1.99 for six populations, and greater than 2.0 for five populations. We observed five populations of duikers with negative trends in point abundances, although only one trend was significant and point abundance estimates for three populations were above 2.0 in the final survey year. Six populations showed positive trends in point abundance (three significant), and the remaining populations displayed no trends. Average occupancy was high (Ψ > 0.60) except for three populations. While literature indicates that historical population declines have occurred, most duiker populations appear relatively healthy in monitored parks. Our results indicate that these parks are effective in protecting most duikers despite hunting pressure. We recommend that systematic, standardized camera-trap monitoring be initiated in other African parks in combination with point-abundance models to objectively assess forest ungulate population trends.

Encouraging encounters: unusual aggregations of bowhead whales Balaena mysticetus in the western Fram Strait
Boer, M.N. de; Janinhoff, N. ; Nijs, G. ; Verdaat, H. - \ 2019
Endangered Species Research 39 (2019). - ISSN 1863-5407 - p. 51 - 62.
Bowhead whale - Balaena mysticetus - Svalbard stock - Abundance - Platform of opportunity - Conservation - Fram Strait
The subpopulation of the bowhead whale Balaena mysticetus in the East Greenland-Svalbard-Barents Sea is endangered and until recently was believed to number in the tens. Recent studies have suggested that this subpopulation appears to be increasing. Here, we report on unusual aggregations of bowhead whales within the Fram Strait. We present opportunistic and effort-corrected observations of bowhead whales made from a small expedition vessel during
cruises in June (2015−2018). Bowhead whales were sighted on 85 occasions (220−227 whales). An aggregation in 2015 (n = 84 whales) and high numbers in 2018 (n = 104−110) exceeded all previous records. The index of whale abundance was significantly higher in open water-leads (1.08−1.14 whales km−1 of survey effort) compared to areas with drift-ice (0.51−0.53 whales km−1). The highest abundance index was measured in deep waters where the bottom slope was relatively steep. Our findings highlight the temporal and spatial consistency of this species in areas with relatively loose ice cover (open water-leads) and steep slopes. It is unknown how global warming and resultant changes in ice-extent are going to affect bowhead whales within the Strait
and whether they will find new feeding grounds due to an expanding open-ocean habitat. These slopes may become increasingly important to bowhead whales and Arctic top predators as a spring/early summer feeding ground. These relatively large numbers of bowhead whales are encouraging and can help direct future research monitoring programs to study the population ecology of these endangered whales.
Beyond scarcity perspectives on energy transition
Geerts, Robert Jan - \ 2018
Relations 6 (2018)1. - ISSN 2283-3196 - p. 49 - 68.
Abundance - Energy debates - Energy discourse - Energy ethics - Energy transition - Good life - Prosperity - Quality of life - Scarcity - Simplicity

Two dominant lines of reasoning in the philosophical debate on energy transition can be described as boundless consumerism (we should find ways to keep growing) and eco-frugality (we should reduce our impact as much as possible). This paper problematizes both approaches via their implicit understanding of the good life, and proposes a third alternative: qualitative abundance. Society is not interested in any sustainable energy system, but in one that caters to our needs and enables us to flourish as human beings. Because the dominant lines in the current debate share a concern for scarcity, they fail to raise the question of a "good" energy system, and therefore the possibility of a positive energy ethics. Qualitative abundance initiates discourse around prosperity (with boundless consumerism) and simplicity (with ecofrugality), thus expanding and enriching debates on energy transition.

Spatio-temporal distribution of mosquitoes and risk of malaria infection in Rwanda
Hakizimana, Emmanuel ; Karema, Corine ; Munyakanage, Dunia ; Githure, John ; Mazarati, Jean Baptiste ; Tongren, Jon Eric ; Takken, Willem ; Binagwaho, Agnes ; Koenraadt, Constantianus J.M. - \ 2018
Acta Tropica 182 (2018). - ISSN 0001-706X - p. 149 - 157.
Abundance - Entomological inoculation rate - Rwanda - Sporozoite rate - Vector distribution
To date, the Republic of Rwanda has not systematically reported on distribution, diversity and malaria infectivity rate of mosquito species throughout the country. Therefore, we assessed the spatial and temporal variation of mosquitoes in the domestic environment, as well as the nocturnal biting behavior and infection patterns of the main malaria vectors in Rwanda. For this purpose, mosquitoes were collected monthly from 2010 to 2013 by human landing catches (HLC) and pyrethrum spray collections (PSC) in seven sentinel sites. Mosquitoes were identified using morphological characteristics and PCR. Plasmodium falciparum sporozoite infection rates were determined using ELISA. A total of 340,684 mosquitoes was collected by HLC and 73.8% were morphologically identified as culicines and 26.2% as anophelines. Of the latter, 94.3% were Anopheles gambiae s.l., 0.4% Anopheles funestus and 5.3% other Anopheles species. Of An. gambiae s.l., An. arabiensis and An. gambiae s.s. represented 84.4% and 15.6%, respectively. Of all An. gambiae s.l. collected indoor and outdoor, the proportion collected indoors was 51.3% in 2010 and 44.9% in 2013. A total of 17,022 mosquitoes was collected by PSC of which 20.5% were An. gambiae s.l. and 79.5% were culicines. For the seven sentinel sites, the mean indoor density for An. gambiae s.l. varied from 0.0 to 1.0 mosquitoes/house/night. P. falciparum infection rates in mosquitoes varied from 0.87 to 4.06%. The entomological inoculation rate (EIR) ranged from 1.0 to 329.8 with an annual average of 99.5 infective bites/person/year. This longitudinal study shows, for the first time, the abundance, species composition, and entomological inoculation rate of malaria mosquitoes collected throughout Rwanda.
Exploring the relationships between landscape complexity, wild bee species richness and reproduction, and pollination services along a complexity gradient in the Netherlands
Bukovinszki, Tibor ; Verheijen, Joke ; Zwerver, S. ; Klop, Esther ; Biesmeijer, Jacobus C. ; Wäckers, Felix L. ; Prins, Herbert H.T. ; Kleijn, David - \ 2017
Biological Conservation 214 (2017). - ISSN 0006-3207 - p. 312 - 319.
Abundance - Floral resources - Landscape intensification - Pollination - Reproduction - Wild bees

Pollinator communities exhibit variable responses to changing landscape composition. A general expectation is that a decreasing cover of semi-natural habitats negatively affects pollinator reproduction, population size and pollination services, but few studies have investigated the simultaneous effects of landscape complexity on different aspects of pollinator communities and functioning. In 20 agricultural landscape plots the size of an average Dutch farm, we studied how changing landscape complexity affected wild bee abundance, species richness and reproduction. To measure pollination, we placed potted strawberry plants as phytometers in landscapes. Landscape complexity was characterized as the area of semi-natural habitats. In addition, we estimated floral resource abundance in each landscape plot. We expected that i) bee species richness, reproduction and pollination would be positively related to area of semi-natural habitats and flower abundance, and that ii) species richness and reproduction would be positively related to pollination. An increase in semi-natural habitats in landscapes increased both the abundance of cavity-nesting bees colonizing trap nests, and the growth rates of experimental Bombus terrestris L. colonies, but not the species richness of wild bees measured by pan traps. There was only a tendency for higher pollination levels of strawberry plants with higher cover of semi-natural habitats. There was no relationship between species richness and bee reproduction in a landscape and the pollination services. Estimated flower abundance in landscape had a positive effect on bumblebee colony growth only and not on the other variables. Our results suggest that, by improving habitat quality on their farms through establishing more semi-natural habitats or enhancing the flower availability in semi-natural habitats, farmers can promote reproduction of a number of functionally important bee species and the pollination services they provide. Bee species richness, however, seems to be more difficult to enhance and requires more than just creating more of the same type of habitats or flowers.

The stretched exponential as one of the alternatives for the power law to fit ranked species abundance data
Straatsma, G. ; Egli, S. - \ 2017
Matters (2017). - ISSN 2297-8240
Species - Abundance - Distribution - Stretched - Exponential
A central object in community ecology is the species abundance distribution, SAD. We are interested in the power law and its allies for ranked species abundance data. We collected 12 large data sets consisting of many samples. The preliminary fitting result makes a robust impression (12 systems at three scales of integration) that the stretched exponential is an interesting alternative for the power law. For further work advanced statistics are required. Not only ‘our’ data but, quite often, other data as well, consist of sample × species cross tables. With cross tables, also 'within species over samples' characteristics can be studied. An integrated view on data-patterns in multi-sample sets may help to identify generative processes for and the formulation of a relatively simple model for species abundance data.
Wild harvest : Distribution and diversity of wild food plants in rice ecosystems of Northeast Thailand
Cruz-Garcia, G.S. ; Struik, P.C. ; Johnson, D.E. - \ 2016
NJAS Wageningen Journal of Life Sciences 78 (2016). - ISSN 1573-5214 - p. 1 - 11.
Abundance - Ecosystem services - Food security - Paddy fields - Rice farmer - Seasonality - Southeast Asia - Spatial structure - Weed

Rice fields provide not only a staple food but are also bio-diverse and multi-functional ecosystems. Wild food plants are important elements of biodiversity in rice fields and are critical components to the subsistence of poor farmers. The spatial and seasonal distribution of wild food plants were analysed across different sub-systems occurring within paddy ecosystems in two adjacent rice farming villages in Kalasin, Northeast Thailand. Data were collected in 102 sampling sites corresponding to seven sub-systems including tree rows, mounds, field margins, shelters, ponds, pond margins and levees. Frequency of occurrence and absolute abundance were quantified for each species in the two seasons of two years, and data on uses of wild food plant species were collected through focus group discussions. A total of 42 species from 28 botanical families were reported, and one third of these have been classified as weeds of rice by other authors. Results show that species abundance, frequency of occurrence and diversity varied seasonally and spatially within paddy rice ecosystems. Higher diversity indexes were observed in the monsoon in most sub-systems. The most diverse sub-systems in the monsoon were shelters, mounds and pond margins, and tree rows and mounds in the dry season. Field margins, ponds and levees presented lower diversity, but are habitat of aquatic species important for the local diet, such as Ipomoea aquatica and Marsilea crenata. The herbs Lobelia sp. and Glinus oppositifolius, classified as rice weeds, were most abundant species in the dry season and frequently consumed. Leucaena leucocephala, of which the roots, leaves and fruits are commonly consumed as vegetable, was the most abundant tree in most sub-systems. More than half of the species were specific to one or two sub-systems due to particular niche requirements. Three quarters of wild food plant species had additional uses besides food; with ten different types of use and multiple use categories occurring in the different sub-systems. This study highlights that the development of more productive lowland rice systems may jeopardize the diversity of wild food plant species in the rice landscape, which is important for the food security of the rural poor.

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