Staff Publications

Staff Publications

  • external user (warningwarning)
  • Log in as
  • language uk
  • About

    '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.

    We have a manual that explains all the features 

Current refinement(s):

Records 1 - 20 / 46

  • help
  • print

    Print search results

  • export

    Export search results

  • alert
    We will mail you new results for this query: keywords==ecological disturbance
Check title to add to marked list
Space-time monitoring of tropical forest changes using observations from multiple satellites
Hamunyela, Eliakim - \ 2017
Wageningen University. Promotor(en): Martin Herold, co-promotor(en): Jan Verbesselt. - Wageningen : Wageningen University - ISBN 9789463436403 - 188
tropical forests - monitoring - satellites - deforestation - ecological disturbance - tropische bossen - satellieten - ontbossing - ecologische verstoring

Forests provide essential goods and services to humanity, but human-induced forest disturbances have been on ongoing at alarming rates, undermining the capacity for forests to continue providing essential goods and services. In recent years, the understanding of the short-term and long-term impacts of deforesting and degrading forest ecosystems has improved, and global efforts to reduce forest loss are ongoing. However, in many parts of the globe, significant forest areas continue to be lost. To fully protect forest ecosystems efficiently, timely, reliable and location-specific information on new forest disturbances is needed. Frequent and large-area forest mapping and monitoring using satellite observations can provide timely and cost-effective information about new forest disturbances. However, there are still key weaknesses associated with existing forest monitoring systems. For example, the capacity for forest monitoring systems to detect new disturbances accurately and timely is often limited by persistent cloud cover and strong seasonal dynamics. Persistent cloud can be addressed by using observations from multiple satellite sensors, but satellite sensors often have inter-sensor differences which make integration of observations from multiple sensors challenging. Seasonality can be accounted for using a seasonal model, but image time series are often acquired at irregular intervals, making it difficult to properly account for seasonality. Furthermore, with existing forest monitoring systems, detecting subtle, low-magnitude disturbances remains challenging, and timely detection of forest disturbances is often accompanied by many false detections. The overall objective of this thesis is to improve forest change monitoring by addressing the key challenges which hinders accurate and timely detection of forest disturbances from satellite data. In the next paragraphs, I summarise how this thesis tackled some of the key challenges which hamper effective monitoring of forest disturbances using satellite observations.

Chapter 2 addresses the challenge of seasonality by developing a spatial normalisation approach that allows us to account for seasonality in irregular image time series when monitoring forest disturbances. In this chapter, I showed that reducing seasonality in image time series using spatial normalisation leads to timely detection of forest disturbances when compared to a seasonal model approach. With spatial normalisation, near real-time forest monitoring in dry forests, which has been challenging for many years, is now possible. Applying spatial normalisation in areas where evergreen and deciduous forests co-exist is however challenging. Therefore, further research is needed to improve the spatial normalisation approach to ensure that it is applicable to areas with a combination of different forest types. In particular, a spatial normalisation approach which is forest type-specifics is desirable. In this chapter, forest disturbances were detected by analysing single pixel-time series. Spatial information was only used to reduce seasonality.

Taking in account the fact that forest disturbances are spatio-temporal events, I investigated whether there is an added-value of combining both spatial and temporal information when monitoring forest disturbances from satellite image time series. To do this, I first developed a space-time change detection method that detects forest disturbances as extreme events in satellite data cubes (Chapter 3). I showed that, by combining spatial and temporal information, forest disturbances can still be detected reliably even with limited historical observations. Therefore, unlike approaches which detect forest disturbances by analysing single pixel- time series, the space-time approach does not require huge amount of historical images to be pre-processed when monitoring forest disturbances. I then evaluated the added-value of using space-time features when confirming forest disturbances (Chapter 4). I showed that using a set of space-time features to confirm forest disturbances enhance forest monitoring significantly by reducing false detections without compromising temporal accuracy. With space-time features, the discrimination of forest disturbances from false detections is no longer based on temporal information only, hence providing opportunity to also detect low-magnitude disturbances with high confidence. Based on the analysis for conditional variable importance, I showed that features which are computed using both spatial and temporal information were the most important predictors of forest disturbances, thus enforcing the view that forest disturbances should be treated as spatio-temporal in order to improve forest change monitoring.

In Chapter 2 – 4, forest disturbances where detected from medium resolution Landsat time series. Yet, recent studies showed that small-scale forest disturbances are often omitted when using Landsat time series. In Chapter 5, I investigated whether detection of small-scale forest disturbances can be improved by using the 10m resolution time series from recently launched Sentinel-2 sensor. I also investigated whether the spatial normalisation approach developed in Chapter 2 can be used to reduce inter-sensor differences in multi-sensor optical time series. I showed that the 10m resolution Sentinel-2 time series improves the detection of small-scale forest disturbances when compared to 30m resolution. However, the 10m resolution does not supersede the importance of frequent satellite observations when monitoring forest disturbances. I also showed that spatial normalisation approach developed in Chapter 2 can reduce inter-sensor differences in multi-sensor optical time series significantly to generate temporally consistent time series suitable for forest change detection. Spatial normalisation does not completely remove inter-sensor differences, but the differences are significantly reduced.

Monitoring of forest disturbances is increasingly done using a combination of Synthetic Aperture Radar (SAR) and optical time series. Therefore, Chapter 6 investigated whether the spatial normalisation approach developed in Chapter 2 can also reduce seasonal variations in SAR time series to facilitate the integration of SAR-optical time series for forest monitoring in dry tropical forests. This Chapter demonstrated that seasonal variations in SAR time series can also be reduced through spatial normalisation. As a result, observations from SAR and optical time series were combined to improve near real-time forest change detection in dry tropical forest. In Chapter 7, it is demonstrated that spatial normalisation has potential to also reduce inter-sensor differences in SAR-optical time series, resulting into temporally consistent SAR-optical time series.

In conclusion, this thesis developed a space-time forest monitoring framework that addresses some key challenges affecting satellite-based forest monitoring. In particular, new methods that allow for timely and accurate detection of forest disturbances using observations from multiple satellites were developed. Overall, the methods developed in this research contribute to our capacity to accurately and timely detect forest disturbances in both dry and humid forests.

Natuurbrug Laarderhoogt en woningbouw op Crailo-Zuid : programma van eisen voor woningbouw nabij de Natuurbrug vanuit ecologisch perspectief
Grift, E.A. van der; Lammerstma, D.R. - \ 2017
Wageningen : Wageningen Environmental Research (Wageningen Environmental Research rapport 2799) - 31
habitatfragmentatie - natuur - kwaliteit - ecologische verstoring - woningbouw - habitatverbindingszones - wildpassages - noord-holland - habitat fragmentation - nature - quality - ecological disturbance - house building - habitat corridors - wildlife passages
Food from the Sulawesi Sea, the need for integrated sea use planning
Siahainenia, Audrie J. - \ 2016
Wageningen University. Promotor(en): Herbert Prins; Johan Verreth, co-promotor(en): Fred de Boer. - Wageningen : Wageningen University - ISBN 9789462578869 - 180
mangroves - mangrove forests - fishes - habitats - marine areas - marine environment - fish stocks - environmental management - ecological disturbance - disturbance - sulawesi - mangrovebossen - vissen - mariene gebieden - marien milieu - visstand - milieubeheer - ecologische verstoring - verstoring - celebes

Mangroves occur in the tropics and subtropics region and an important coastal habitat for the artisanal fisheries along the coast of Indonesia. Around 19% of the total mangrove area in the world is located in Indonesia. Besides providing a barrier against coastal/Delta erosion, mangrove forest plays a significant role as a nursery area for most of the marine communities. Unluckily, 57% of the ±3.2 million ha of the mangroves in Indonesia is currently in degraded, mostly because of human activities (anthropogenic disturbance). The primary sources of anthropogenic disturbances to mangroves are increasing population growth rate and demand for seafood products as an essential protein, especially the wild shrimp, in the world market. These resulted in land-use conversion along estuarine areas not only for settlements and plantations but also for aquaculture ponds. The lack of awareness and understanding of the value and function of mangrove ecosystems contributed to the loss and damage the mangroves area.

Therefore, my research and field experiment aimed to quantify the effects of human disturbance on mangroves associated trophic cascades in Indonesia estuarine areas. The study was performed in the Berau District, East Kalimantan, Indonesia between 2005 and 2010. Data of mangrove extent from 1990 in the Berau Delta was used as base data with low human disturbance. We also interviewed the artisanal fishermen about their catches, origins, and fishing locations, in relation to the total catch per unit effort (CpUE).

The results had shown that the total mangroves area in the Berau Delta decreased by 54% between the 1990 and 2009, which led to fragmentation and alteration in the structural complexity of mangroves. The field experiment conducted at three locations with different levels of human disturbances revealed that the species richness was decreased with increased the level of human interference and the marine community tended to be dominated by only a few species. In the highly disturbed areas, the catch of small-scale fishermen tended to be lower. Furthermore, the result from a spatial statistical model indicated that the disturbance of mangrove habitats was influenced the distribution pattern of shrimp. The total CpUE of small-scale fishery in the study area was relatively small, and the area was probably not overexploited.

As a conclusion, mangroves habitat in the Berau Delta played a significant role in sustaining coastal fisheries. This important ecosystem supports a primary source of marine protein. Mangrove forests can only guarantee these marine resources if the people consciously maintain its viability through a strong management policy.

Review van ecologische probleembeschrijvingen voor het Eems estuarium
Baptist, M.J. ; Tamis, J.E. - \ 2015
Den Burg : IMARES (Rapport / IMARES Wageningen UR C076/15) - 31
ecologisch herstel - herstelbeheer - estuaria - ecologische verstoring - waterkwaliteit - aquatische ecologie - eems-dollard - ecological restoration - restoration management - estuaries - ecological disturbance - water quality - aquatic ecology
Het Eems estuarium heeft al geruime tijd te kampen met ecologische problemen van diverse aard. In het Bestuurlijk Overleg MIRT (Meerjarenprogramma Infrastructuur, Ruimte en Transport) NoordNederland in het najaar van 2013, is afgesproken dat rijk en regio een MIRT-onderzoek Eems-Dollard starten. Het rijk en de provincie Groningen zijn gezamenlijk de opdrachtgevers voor dit onderzoek. Het doel van het MIRT-onderzoek is het voorbereiden van keuzes rondom de Nederlandse strategie in de bilaterale samenwerking met Duitsland, gericht op het ecologisch behoud en herstel van het EemsDollard estuarium in balans met kustveiligheid, ruimtelijke kwaliteit en economische ontwikkeling. Dit rapport maakt deel uit van MIRT-onderzoek Eems-Dollard Fase II spoor 1, het ecologische kennisspoor. Het bouwt voort op resultaten uit MIRT-onderzoek Fase I en andere bestaande probleembeschrijvingen. Dit rapport is het resultaat van een reviewstudie van ecologische probleembeschrijvingen voor het Eemsestuarium.
Hoe kan het dat ons drinkwater opraakt?
Vet, L.E.M. - \ 2015
Universiteit van Nederland
watervoorziening - zoet water - aquatische ecosystemen - eutrofiëring - lesmaterialen - ecologische verstoring - fosfaat - ecologisch herstel - water supply - fresh water - aquatic ecosystems - eutrophication - teaching materials - ecological disturbance - phosphate - ecological restoration
Er is te weinig zoet water voor de mensheid. Dat is niet gek als je bedenkt dat je om kilo rundvlees te produceren al 15.500 liter water nodig hebt. Wat kunnen we daar aan doen? Daarover vertelt prof. dr. Louise Vet van Wageningen UR, directeur NIOO, in dit college.
Seal monitoring and evaluation for the Luchterduinen offshore wind farm: 2. Tconstruction - 2014 report
Kirkwood, R.J. ; Aarts, G.M. ; Brasseur, S.M.J.M. - \ 2015
Den Helder : IMARES (Rapport / IMARES Wageningen UR C152/14) - 65
zeehonden - habitats - halichoerus grypus - phoca vitulina - menselijke invloed - windmolenpark - constructie - monitoring - ecologische verstoring - noordzee - zuid-holland - seals - human impact - wind farms - construction - ecological disturbance - north sea
Two seal species live in Dutch waters: the harbour seal (Phoca vitulina) and the grey seal (Halichoerus grypus). They occupy land-based sites (haul-outs) in both the Wadden Sea and the Delta region, and move between these regions along the North Sea coastal zone. Human activities, such as construction of a wind farm in this zone, may influence movement and use of the zone by the seals. Monitoring of potential impacts on seals to Luchterduinen construction was required in the permit to construct. The Luchterduinen offshore wind farm is the third wind farm development in the Dutch North Sea coastal zone (between Den Helder and Rotterdam). Pile-driving of the turbine towers occurred between 31 July and 16 October, 2014. Seals exposed to pile-driving, even at close distances of
A safe operating space - Terry Hughes
Wageningen UR, - \ 2015
Wageningen : Wageningen UR
ecosystemen - ecologische verstoring - natuurreservaten - klimaatverandering - maatregelen - ecosystems - ecological disturbance - nature reserves - climatic change - measures
Mondiaal beeldbepalende ecosystemen zoals het Groot Barrière Rif en het Amazonewoud lopen het risico op instorting door klimaatverandering. Dat risico kan echter fors worden verkleind door lokale maatregelen zoals het inperken van overbevissing, vervuiling en boskap, zo stelt een internationaal team van wetenschappers onder leiding van Marten Scheffer van Wageningen University in Science van 20 maart 2015
Webinar Msc Forest and Nature Conservation
Wageningen UR, ; Scheffer, M. - \ 2014
Wageningen UR
ecosystemen - ecologische verstoring - natuurreservaten - klimaatverandering - maatregelen - plaatselijke planning - ecosystems - ecological disturbance - nature reserves - climatic change - measures - local planning
Mondiaal beeldbepalende ecosystemen zoals het Groot Barrière Rif en het Amazonewoud lopen het risico op instorting door klimaatverandering. Dat risico kan echter fors worden verkleind door lokale maatregelen zoals het inperken van overbevissing, vervuiling en boskap, zo stelt een internationaal team van wetenschappers onder leiding van Marten Scheffer van Wageningen University in Science van 20 maart 2015
Natuurbrug Laarderhoogt en oefencentrum Crailo : ecologische toetsing van plannen voor een oefencentrum voor brandbestrijding nabij de natuurbrug
Grift, E.A. van der; Lammertsma, D.R. - \ 2014
Wageningen : Alterra, Wageningen-UR (Alterra-rapport 2553) - 41
brandbestrijding - oefening - ecologische verstoring - wildpassages - natuurgebieden - het gooi - noord-holland - fire fighting - practice - ecological disturbance - wildlife passages - natural areas
In opdracht van de Veiligheidsregio Gooi en Vechtstreek is onderzocht wat de aanleg van een oefencentrum voor brandbestrijding op het voormalige AZC-terrein nabij rijksweg A1 betekent voor het ecologisch functioneren van de hier geplande natuurverbinding met Natuurbrug Laarderhoogt. Er is ook onderzocht welke maatregelen eventuele negatieve effecten op het functioneren van het ecoduct kunnen mitigeren dan wel opheffen.
Handreiking voor het berekenen van een ecologische voetafdruk : eindrapport KBIV WOt 2013
Verzandvoort, S.J.E. ; Arets, E.J.M.M. ; Hack-ten Broeke, M.J.D. - \ 2014
Wageningen : Alterra, Wageningen-UR (Alterra-rapport 2554) - 91
landgebruik - watergebruik - ecologische verstoring - productieprocessen - consumptiepatronen - inventarisaties - land use - water use - ecological disturbance - production processes - consumption patterns - inventories
Dit rapport geeft een raamwerk voor het bepalen van een ecologische voetafdruk voor veranderingen in productie- en consumptiesystemen. Het raamwerk kan worden gebruikt voor het bepalen van benodigd land- en watergebruik voor productie van goederen en diensten.
De ecologische achtergrond van de crisis
Lyklema, J. - \ 2013
Civis Mundi (2013). - ISSN 0030-3283 - 9
natuurlijke hulpbronnen - economische analyse - ruwe grondstoffen - duurzaamheid (sustainability) - ecologische verstoring - natural resources - economic analysis - raw materials - sustainability - ecological disturbance
Het recente gebeuren met de Fyra illustreert weer eens dat het progressief moeilijker wordt significante verbeteringen op infrastructureel niveau te realiseren. Deze talrijke dagelijks waarneembare afgeleide symptomen van het ecologische probleem worden door de politiek vaak als het probleem gezien, en dus gaat de politiek daar wat aan doen. Symptoombestrijding heet dat. Echter, op zijn hoogst kunnen deze manipulaties een deel van de problemen tijdelijk vooruit schuiven ten koste van een vergroting van de problemen op langere termijn. Feitelijk leiden ze tot een vergroting van de huidige crisis doordat telkens een extra hypotheek wordt genomen op de eindige ecologische gebruiksruimte.
Het Monitoring en Evaluatie Programma Zandwinning RWS LaMER 2007 en 2008 - 2012: overzicht, resultaten en evaluatie
Rozemeijer, M.J.C. ; Kok, J. ; Ronde, J. de; Kabuta, S. ; Marx, S. ; Berkel, G. van - \ 2013
IJmuiden : IMARES (Rapport / IMARES Wageningen UR C181/13) - 116
zandafgravingen - mariene gebieden - mariene ecologie - watervogels - zeehonden - nadelige gevolgen - milieueffectrapportage - ecologische verstoring - sand pits - marine areas - marine ecology - waterfowl - seals - adverse effects - environmental impact reporting - ecological disturbance
Zandwinning en -transport kunnen potentieel leiden tot diverse effecten zoals verminderde productie van algen en schelpdieren door extra slib in de waterkolom en verstoring. Geschatte effecten van zandwinning volgens de MERren. Visuele verstoring van zeehonden en vogels: de dieren worden verstoord doordat ze de sleephopperzuiger zien en reageren door bv weg te vluchten en andere vormen van onrust wat kan resulteren in (tijdelijke) effecten op de conditie van het dier en zelfs voortplanting en populatiedynamica. Geluidverstoring van vissen, vogels en zeezoogdieren: geluid wordt geproduceerd tijdens het baggeren op de winlocatie en tijdens het varen, waarbij de geluidsbron zich verplaatst. Verstoringseffecten kunnen ook optreden door het geluid tijdens baggeren (zowel boven als onderwater). Dit heeft op hoofdlijnen het zelfde effect als visuele verstoring maar via een andere effectroute.
African wildlife and people : finding solutions where equilibrium models fail
Poshiwa, X. - \ 2013
Wageningen University. Promotor(en): Herbert Prins; Ekko van Ierland, co-promotor(en): Ignas Heitkonig; Rolf Groeneveld. - Wageningen : Wageningen UR - ISBN 9789461737618 - 173
wild - extensieve weiden - evenwicht - droogte - mensen - herbivoren - vee - verstoring - ecologische verstoring - zimbabwe - afrika - wildlife - rangelands - equilibrium - drought - people - herbivores - livestock - disturbance - ecological disturbance - africa

Grazing systems, covering about half of the terrestrial surface, tend to be either equilibrial or non-equilibrial in nature, largely depending on the environmental stochasticity.The equilibrium model perspective stresses the importance of biotic feedbacks between herbivores and their resource, while the non-equilibrium model perspective stresses stochastic abiotic factors as the primary drivers of vegetation and herbivore dynamics.In semi-arid and arid tropical systems, environmental stochasticity is rather high, making the systems essentially non-equilibrial in nature, suggesting that feedback between livestock and vegetation is absent or at least severely attenuated for much of the time. In southern Africa, range and livestock management however, has been built around the concept of range condition class and the practices of determining carrying capacities and manipulating livestock numbers and grazing seasons to influence range condition. This management approach is derived from the equilibrium or climax concept of Clementsian succession. The erratic and variable rainfall in many pastoral areas of Africa poses a fundamental challenge to this conventional notion of carrying capacity in range management. This realization has caused a shift towards models that embrace non-equilibrium dynamics in ecosystems. The main concern is that application of the range model may contribute to mismanagement and degradation of some rangeland ecosystems. However, only a few studies in rangelands have empirically tested the non-equilibrium hypothesis leading to the debate on rangeland dynamics remaining unresolved.

Across the savannas of Africa, grasslands are being changed into cultivation due to increasing human population, at the expense of decreasing wildlife populations. African savannas however, still contain pockets of wilderness surviving as protected areas, but even there, species richness of large mammals is decreasing. The inevitable result is the loss of most of the wild plants and animals that occupy these natural habitats, at the same time threatening the well-being of the inhabitants of these savannas. Hence, to facilitate the management of arid and semi-arid savannas for both biological conservation and sustainable use (improving human welfare) an improved understanding of the complex dynamics of these savannas is critical. Furthermore, it is widely recognized that a high level of uncertainty typifies the lives of rural farmers in developing countries.Non-equilibrium dynamics bring additional uncertainty and risk to the system.However, attempts to understand efficient and sustainable ways to improve biodiversity and human welfare in systems showing non-equilibrium dynamics have been rare.The behaviour of non-equilibrium systems is characterised as more dynamic and less predictable than equilibrium systems. Therefore, non-equilibrium dynamics in dryland ecosystems present a different kind of management problem for both livestock and wildlife systems since their management has been dictated by the equilibrium assumption. Additionally, loss of biodiversity is regarded today as one of the great unsolved environmental problems.Faced with this biodiversity crisis, the challenge is to find ways to respond in a flexible way to deal with uncertainty and surprises brought about by non-equilibrium dynamics.

In this thesis I use a bioeconomic approach in analyzing the implications of non-equilibrium dynamics for the efficient and sustainable management of wildlife and livestock in dryland grazing systems. The study area for this thesis is southeastern lowveld of Zimbabwe.

In chapter 2, I investigate the role of abiotic and biotic factors in determining plant species composition. While early studies emphasized the importance of edaphic and environmental controls on plant species distribution and spatial variation in vegetation composition, recent studies have documented the importance of both natural and anthropogenic disturbances in this respect. At a regional scale vegetation structure (i.e., grass/tree ratio) and species composition in savannas is largely determined by precipitation, whereas at the nested landscape-scale vegetation structure and composition is more prominently determined by geologic substrate, topography, fire and herbivory. Chapter 2, shows that at the landscape scale, abiotic variables such as rainfall and soil fertility override the effect of humans and livestock on the herbaceous and the woody plant composition.

Then, in Chapter 3, I ask the question whether there is something like non-equilibrium and what are the impacts of such dynamics on cattle herd dynamics? I studied the relevance of non-equilibrium theory to my study area by testing whether annual changes in cattle numbers showed the presence of crashes and if so, what were the factors best explaining those crashes and what age and sex classes of cattle were most vulnerable to such crashes? Chapter 3 showed that crashes in annual cattle numbers were evident and were best explained by rainfall and NDVI and their lags. Immigration i.e., movement in of animals was also an important factor in years when rainfall was below the threshold and so it was a possible source of cattle recovery after a crash together with high calving rates. In years when rainfall was above the rainfall threshold, NDVI explained more variation in annual changes of livestock. The impacts of crashes were greater on calves than other cattle age categories thus explaining why there are legacy effects (lags) in cattle numbers that can only partly be offset by cattle purchases from elsewhere because of poverty or lack of surplus stock elsewhere. These findings make the southeastern lowveld system to be dominated by non-equilibrium dynamics.

The welfare of local people is the issue that I focused on in my economic section of this thesis (Chapters 4 and 5). I addressed the question of how risks of fluctuations in household income can be managed in order to improve human welfare. The expectation was that in systems exhibiting non-equilibrium dynamics people can improve their welfare by exploiting a combination of wildlife and agricultural activities (livestock and cropping) in their attempts to reduce fluctuations in their annual welfare. This would be possible if the risks in wildlife and agro-pastoral systems were sufficiently different. Exploiting different sources of income requires efficient allocation of resources. The most prominent resource is land and land varies spatially in quality and ecological resources require spatial connectivity. Therefore the spatial dimension is important in this allocation.

In Chapter 4 I asked the question: To what extent can wildlife income buffer rural households’ incomes against fluctuations in rainfall? I studied the extent to which wildlife derived income can buffer local households’ income against fluctuations due to rainfall. The addition of wildlife as an asset for rural farmers’ portfolio of assets showed that wildlife can be used as a hedge asset to offset risk from agricultural production without compromising on return. However, the power of diversification using wildlife is limited because revenues from agriculture and wildlife assets were positively correlated. However, the correlation was very weak (only 0.4 and the explained variance thus only be 16 %) which gives ample scope for buffering. Therefore, revenues from wildlife have potential to reduce household income fluctuations due to drought, but only to a limited extent.

In Chapter 5 the question was: From a theoretical perspective, can wildlife income have an insurance value to local people? I used a modelling approach to study the extent to which wildlife income offers an insurance value to local people against fluctuating annual rainfall. Findings did not support the common assertion that wildlife can offer insurance to local people against income fluctuations due to rainfall fluctuations. The failure by wildlife income to offer insurance value to local people could be explained by high costs of harvesting the wildlife resource and high densities of both human and livestock populations in southeastern lowveld.As corollary I draw the conclusion that wildlife cannot pay its way in these rangelands as long as there are high densities of people as shown in Chapter 5. Definitely wildlife income becomes insufficient if long-term sustainability of wildlife resources is considered.

Chapter 6, finally synthesizes the conclusions that can be drawn from the preceding chapters and puts the issues addressed in a broader context. In summary, this thesis shows evidence of non-equilibrium dynamics in semi-arid grazing systems. Furthermore, the small contribution of wildlife income to local people’s welfare goes to show the widely shared view that financial rewards generated through integrated conservation and development programmes such as CAMPFIRE have generally been seen as insufficient. This led me to suggest that if we have a moral or ethical obligation to protect wildlife species, then an important way for people to meet their aspirations economically was suggested by Malthus.

Disturbance and recovery of litter fauna: a contribution to environmental conservation
Comor, V.N.R. - \ 2013
Wageningen University. Promotor(en): Herbert Prins; Steven Bie, co-promotor(en): Frank van Langevelde. - S.l. : s.n. - ISBN 9789461737496 - 114
bodemfauna - bodemverstoring - ecologische verstoring - gemeenschappen - ecologisch herstel - ecosystemen - bodemecologie - milieubeheer - natuurbescherming - soil fauna - soil disturbance - ecological disturbance - communities - ecological restoration - ecosystems - soil ecology - environmental management - nature conservation

Disturbances play a great role in ecosystem functioning and, with the increasing anthropogenic activities, they have more and more influence on ecosystems. They have been studied for several decades but recovery, the ecological phenomenon following a disturbance, has seldom been the focus of research. In this thesis, I studied the impact of disturbances on the structure of soil and litter fauna communities and their ensuing recovery in varying environmental conditions, combined with the effect of productivity, life-history traits and community structure. I combined all the results to draw some conclusions on the main factors involved in recovery, how to improve recovery of ecosystems and how to make better predictions on recovery.

In the second chapter of this thesis, I studied how the structure of soil and litter fauna communities from two climatically contrasting biomes was affected by a similar disturbance and how these communities recovered. I sampled litter macrofauna in a temperate and a boreal forest and, to be able to determine whether the communities had recovered, I created a “recovery index” that took into account the pre- and post-disturbance conditions of the disturbed and the control communities, taking into account natural variations. I hypothesised that the temperate communities would recover more rapidly due to the warmer temperatures and to higher species richness and abundance. Recovery was as fast in both biomes, which also had similar species richness. Contrary to my assumption, higher pre-disturbance species abundance did not favour the resistance of communities to the disturbance; on the contrary, high-abundance communities suffered a proportionally greater loss than other communities. Analyses based on life-history traits revealed that dispersal capabilities were the most relevant traits for species facing a disturbance and also for re-establishing. An unexpected factor that influenced the outcome of the disturbance was the litter layer, which, thick in the temperate forest and almost inexistent in the boreal one, protected the fauna of this former biome.

The aim of my third chapter was to consider the main two theories of species assembly, the niche and neutral theory, in the context of a recovery. I considered these two theories not as mutually exclusive but as if they were at opposite ends of a stochasticity gradient. The neutral theory predicts recovered communities in a similar environment to be dissimilar from one another and the niche theory predicts the opposite, because, in this case, species assembly is driven by deterministic factors inherent to communities and to the environment. I used the same experiments as in the previous chapters and hypothesised that the more constraining environmental conditions of the boreal forest would lead to a species assembly rather driven by deterministic factors, with recovered communities more similar to each other than the temperate ones. These latter ones, from a less constraining environment, would be more dissimilar to each other. I found that the structure of each community before and one year after the disturbance was indeed more similar in the boreal forest. This would mean that, in low-productivity environments, the response of communities being less variable, it could be more easily predictable.

In Chapter 4, I studied the structure of communities from a different perspective, using the density – body mass (DBM) relationship to detect changes in the structure of communities after a disturbance. I hypothesised that the slope of the relationship would be less steep if smaller organisms were mainly impacted or that it would be steeper if larger organisms were mainly impacted. By collecting the soil and litter fauna before, just after and again one and two months after a disturbance, I could establish that the DBM relationship reflected the changes of the structure of communities responding to modifications of the environment. In disturbed conditions, the slope of the DBM relationship of a community was less steep, because mainly the small organisms were impacted by the disturbance. I also showed that, at the very early stage of the recovery, the slope was even less steep, because of the large body mass of the first colonisers. This study confirmed the necessity to sample a broad spectrum of body masses and it was the first time that the DBM relationship was shown to be able to reflect changes of the structure of communities. I concluded by suggesting that it could be used for environmental biomonitoring.

After the satisfying results of Chapter 4, I decided to test the ability of the DBM relationship to reflect different structures of communities living in environments varying by their productivity and subjected or not to a disturbance. I hypothesised that communities from low-productivity areas would have a less steep slope than high-productivity area communities and that disturbed communities would also have a less steep slope. To test this, soil and litter fauna were collected from a salt marsh at four elevation levels (hence subjected to varying sea inundation frequencies, from daily to annually), half of which were subjected to cattle grazing (i.e., the disturbance). I assumed that the least inundated sites were more productive and used the quantity of plant litter to confirm this. The only significant result was between the daily and annually inundated ungrazed areas, confirming that communities from high-productivity areas have a steeper DBM relationship slope. High productivity does not seem to equally affect all the trophic levels, certainly due to inefficient transfers of energy from one level to the other.

In the synthesis, I suggested that recovery should first be properly defined to establish when a community has reached that stage and I advise to use pre- and post-disturbance states of control communities for that purpose. Besides, several environmental factors have to be taken into account instead of only focusing on one species or one ecosystem service, as I have showed that the species richness and abundance of communities, and the productivity and heterogeneity of the environment can influence the resistance and recovery of ecosystems. I also propose, in a first time, to study species assembly in constraining environments, where stochastic factors are limited, in order to obtain a better mechanistic understanding of the processes involved. As there is yet not such understanding, I suggest that managers in charge of environmental conservation rather use a phenomenological approach to quickly estimate outcomes of recovery.

Natuurbrug Laarderhoogt : ecologische toetsing van plannen voor een Nationaal Tenniscentrum en crematorium nabij de natuurbrug
Grift, E.A. van der; Ottburg, F.G.W.A. - \ 2013
Wageningen : Alterra, Wageningen-UR (Alterra-rapport 2446) - 42
fauna - wildpassages - heidegebieden - migratie - ecologische verstoring - tennis - ecologische hoofdstructuur - nadelige gevolgen - openluchtrecreatie - plaatselijke planning - het gooi - noord-holland - wildlife passages - heathlands - migration - ecological disturbance - ecological network - adverse effects - outdoor recreation - local planning
In opdracht van de provincie Noord-Holland is onderzocht wat de aanleg van een Nationaal Tennis Centrum en een crematorium op het voormalige AZC-terrein nabij rijksweg A1 betekent voor het ecologisch functioneren van de hier geplande Natuurbrug Laarderhoogt. Er is ook onderzocht welke maatregelen eventuele negatieve effecten op het functioneren van het ecoduct kunnen mitigeren dan wel opheffen. Deze natuurbrug is net ten oosten van Bussum gepland en zal hier zowel de rijksweg A1 als de ten noorden daarvan gelegen Naarderstraat overspannen. Deze verbindingszone heeft als doel de natuurgebieden ten zuiden van de rijksweg (o.a. Bussummerheide, Westerheide, Zuiderheide) te verbinden met die ten noorden van de rijksweg (o.a. Blaricummerheide, Tafelbergheide)
Species in a dynamic world: Consequences of habitat network dynamics on conservation planning
Teeffelen, A.J.A. van; Vos, C.C. ; Opdam, P.F.M. - \ 2012
Biological Conservation 153 (2012). - ISSN 0006-3207 - p. 239 - 253.
habitats - ecologische verstoring - natuurbescherming - biodiversiteit - dynamische systemen - ruimtelijke ordening - landgebruiksplanning - soorten - ecological disturbance - nature conservation - biodiversity - dynamic systems - physical planning - land use planning - species - colonization-extinction dynamics - structured metapopulation model - climate-change - landscape dynamics - reserve design - patch dynamics - fragmented landscapes - dependent disturbance - distribution patterns - density regulation
Habitat dynamics (habitat turnover due to natural perturbations or human activity) are commonplace, particularly in intensively used landscapes. Conservation planning requires an understanding of how spatio-temporal habitat dynamics and species characteristics interact with and relate to species persistence. We conducted a systematic literature review to determine how spatial and temporal properties of habitat networks can be changed to improve species viability in dynamic landscapes. We searched for both generalities that can be interpreted as spatial planning guidelines and gaps in knowledge that limit the application in spatial planning. Seventy studies matched our inclusion criteria. From these studies, we extracted knowledge regarding the role of four spatial and five temporal network properties (e.g. network area and habitat turnover rate) for species viability. We found that improving spatial network properties often effectively counterbalances the negative effects of habitat dynamics. Furthermore, changes in several temporal properties can alleviate the impact on species viability, for example, by reducing clustering in habitat turnover events. From these findings, we formulated a first set of general qualitative guidelines for planning practices. Moreover, we identified gaps between the available and required knowledge for planning ecological networks in dynamic landscapes, thereby leading to a research priority list containing the following recommendations: (1) provide guidance regarding the effective management of network properties; (2) compare alternate management regimes and their cost-effectiveness; (3) study management regimes for a wide range of species and habitat properties. Given the continuing climate change and economic development, guiding network design—including habitat dynamics—is urgently needed.
Het storten van bagger in diepe zandwinputten is nadelig voor de visstand
Harmsen, J. ; Bierman, H. ; Zoetemeyer, B. - \ 2012
Visionair : het vakblad van sportvisserij Nederland 15 (2012). - ISSN 1569-7533 - p. 36 - 38.
zandafgravingen - plassen - bagger - baggerspeciedepots - ecologische verstoring - dierenwelzijn - opinies - visstand - aquatische ecologie - mens-dier relaties - sand pits - ponds - dredgings - spoil banks - ecological disturbance - animal welfare - opinions - fish stocks - aquatic ecology - human-animal relationships
Het storten van bagger in diepe zandwinputten lijkt een eenvoudige en goedkope oplossing voor het baggerprobleem. Deze zandwinputten zijn echter ook onderdeel van het leefmilieu voor vissen. Kun je dan zo maar bagger gaan storten? De deskundigen verschillen van mening
Tipping points in natural systems. An inventory of types, early warnings, and consequences
Voorn, G.A.K. van - \ 2012
Wageningen : Wageningen University (Biometris report 20.11.11) - 71
ecosystemen - ecologische verstoring - natuurlijke hulpbronnen - ecosysteemdiensten - menselijke activiteit - vroegtijdige diagnose - ecosystems - ecological disturbance - natural resources - ecosystem services - human activity - early diagnosis
Hoe creatief om te gaan met de toenemende druk door de menselijke populatie en de mogelijke belangenverstrengelingen van verschillende belangenhouders die dat met zich meebrengt, bv. door systemen meerdere functies tegelijk te laten vervullen. Het KB IV-programma “groenblauwe ruimte” beoogt te onderzoeken hoe, door goed gebruik te maken van de half-natuurlijke terrestrische (‘groene’) en aquatische (‘blauwe’) ruimte, hier oplossingen kunnen worden geboden. Onderzoek heeft uitgewezen dat er in meerdere natuurlijke en menselijke systemen mogelijke ‘kantelpunten’ (Eng. ‘tipping points’) bestaan: Kleine veranderingen in factoren die van belang voor het systeem zijn, kunnen onverwacht leiden tot plotselinge grote veranderingen.
Effecten van helicoptervluchten op geringe hoogte boven de Friese kust en Terschelling
Smit, C.J. ; Bemmelen, R.S.A. van; Jong, M.L. de - \ 2010
Texel : IMARES (Rapport / IMARES Wageningen UR C129/10) - 56
helikopters - ecologische verstoring - achteruitgang (deterioration) - milieueffect - milieueffectrapportage - noordzee - verstoring - waddenzee - nederlandse waddeneilanden - helicopters - ecological disturbance - deterioration - environmental impact - environmental impact reporting - north sea - disturbance - wadden sea - dutch wadden islands
Ten behoeve van het Europese Interreg-project CLIWAT is door Vitens gevraagd om een Verstoring- en Verslechteringstoets op te stellen van de effecten van helikoptervluchten langs de randen van de Waddenzee. Het doel van de vluchten was inzicht te verkrijgen in de effecten van klimaatverandering en zeespiegelrijzing op het evenwicht tussen zoet en zout grondwater in gebieden grenzend aan de Noordzee. IMARES heeft in mei 2009, op basis van een door Vitens gegeven beschrijving van de voorgenomen activiteiten, een Verstorings- en Verslechteringstoets opgesteld waarin de voorspelde effecten van helikoptervluchten zijn beschreven en waarin een opsomming wordt gegeven van de ter plaatse aanwezige te beschermen natuurwaarden, één en ander op basis van de kracht zijnde Aanwijzingsbesluiten van de Natura 2000 gebieden Noordzeekustzone, Duinen van Terschelling en Waddenzee.
Lac Bonaire - Restoration Action Spear Points, September 2010
Debrot, A.O. ; Meesters, H.W.G. ; Leon, L. de; Slijkerman, D.M.E. - \ 2010
Den Helder : IMARES (Report / IMARES Wageningen UR nr. C131/10) - 25
zostera - mangroves - ecologische verstoring - natuurbescherming - oplossingen - natuurbeleid - ecological disturbance - nature conservation - solutions - nature conservation policy
Lac Bay is the most important mangrove and sea grass area of Bonaire and has been undergoing steady ecological decline in the last decades. Based on an initial assessment of conservation management issue and potential solutions as conducted by IMARES in June 2010, the Dutch Ministry of Agriculture, Nature and Food Quality (LNV) asked IMARES to return to Bonaire to work with Stinapa Bonaire to choose narrower priorities and jointly make a short-list of topics as a working document for cooperation and action. In the beginning of September 2010, site visits and discussions were held in Bonaire with the manager of Lac Bay and various stakeholders to identify and agree on priority issues for action. This working report gives the results of the visit.
Check title to add to marked list
<< previous | next >>

Show 20 50 100 records per page

 
Please log in to use this service. Login as Wageningen University & Research user or guest user in upper right hand corner of this page.