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Intertidal salt marshes provide a range of valuable ecosystem services which typically increase with marsh width. Understanding the drivers for salt marsh expansion versus retreat is thus key to managers. Previous research highlights the influence of short-term (daily/event) bed level dynamics on germination and establishment and subsequent vegetation presence. However, more recent literature suggests the importance of medium-term seasonal bed level dynamics on viable seed availability and subsequent vegetation presence. This study aims to assess event-based and seasonal bed level dynamics for vegetation presence in natural and semi-natural salt marshes and to provide generic thresholds for vegetation presence. To gain insight into bed level dynamics, data was used from autonomous Optical and Acoustic Surface Elevation Dynamics sensors (O-SED and A-SED) around the edge of natural and semi-natural salt marshes. Sensors were installed at vegetated and unvegetated measurement station Field observations from 22 O-SEDs deployed at 4 well-established natural salt marshes in the Western Scheldt estuary and 4 O-SEDs at a well-established semi-natural salt marsh in the Wadden Sea were reanalyzed. Six novel A-SEDs were deployed at a pioneer semi-natural salt marsh in the Ems-Dollard Estuary. The measurement duration at all salt marshes was at least 1 year. The A-SED sensor was successfully validated against manual measurements. Furthermore, vegetation data and water level data were obtained. No significant difference was observed between natural and semi-natural salt marshes. However, a significant difference between vegetated and unvegetated measurement stations for short-term bed level dynamics was observed. Vegetation was found to be present at locations restricted by short-term bed level variability smaller than or equal to 12 mm, emphasizing the presence of a short-term threshold. Although trends in the non-growing season were significantly different between vegetated an

We studied nearshore diurnal fish catches and fisheries development in the early stages of mangrove rehabilitation around the village of Timbulsloko on the central north coast of Java, Indonesia. Mangrove rehabilitation was part of a Nature-based Solutions project to re-establish ecological and economic resilience by combining coastal engineering measures with ecological recovery in conjunction with sustainable land and resource use. Creel surveys were conducted during the onset of the monsoon season October–December 2017 to document yields of the three main fishing gears targeting mangrove finfish in a 419 ha mangrove backwater basin. These were accompanied by structured interviews to obtain fisher views on developments in these fisheries. Analysis of satellite images and GIS-mapping were used to follow developments in mangrove coverage and effort in the estuarine lift-net fishery. Mangrove recovery between 2005 and 2018 achieved 8.5% of its maximum possible (historic) cover potential in the basin and followed an exponential growth curve. The increase in lift-net installations targeting finfish lagged in comparison to mangrove increase, remaining virtually zero till 2014, after which it rapidly increased. A baseline study in 2015 found no mangrove-associated finfish fisheries occurring in our study area. The 51 fishers surveyed in 2017, indicated that fishing activity in the area had strongly increased since 2015, with 45% of fishers stating to having started fishing this area a year earlier or even more recently. A significant majority of 87% of respondents with more than one year of experience at this location, stated that their catches had changed in terms of either fish size, quantity or composition since they started fishing, while 86% indicated improvement in terms of either size or quantity. Fishing generated about 1.05 ± 1.11 (SD) USD/hr worth of catch to professional fishers using either of the two net-types studied. As per 2017, fishing had become profita

Tussen 1900 en nu wijzigden de natuurambities voor de Waddenzee van natuurbehoud en natuurherstel, via natuurontwikkeling, naar natuurversterking. Dit essay inventariseert recente en geplande natuurversterkingsprojecten in de Waddenzee en geeft een analyse van de motieven. De lijn van veranderende ambities dootrekkend eindigt het met een vooruitblik naar een mogelijke toekomst voor natuurbeheer, waarin de eigenschappen van de Waddennatuur gemodificeerd worden om de gevolgen van klimaatverandering te weerstaan.

Constructed salt marshes as a Nature-Based Solution for coastal defense offer additional benefits over conven- tional engineering, but project realization is often hampered by practical and governmental obstacles. We assessed the execution of a local-scale salt marsh construction project as a Nature-Based Solution (NBS) with respect to the regional-scale Social-Ecological System (SES) in an explicitly linked NBS-SES framework. A local municipality came up with various plans to develop its waterfront but these proved unrealizable without wider stakeholder participation. Crucial for success was that the local initiative was turned into an NBS integrating livability, bio- diversity and flood safety, and that it was linked to the governance systems and actors in a regional SES. The chosen NBS consists of a city beach and two salt marshes, a salt marsh park that is open to the public and a pioneer salt marsh that is only accessible for research. The pioneer salt marsh was constructed by raising the seabed to around mean high tide with sand obtained from a capital dredging project. It was used as a large-scale natural experiment in salt marsh construction. To test the effect of enrichment with silt and clay on initial salt marsh development, six hectare-scale compartments were created in which mud was mixed with sand in the top 1.0 m of the bed to three mud contents of on average 8%, 25% and 48%. Heavy machinery was needed to mix mud through the upper meter of the sandy bed. Mixing mud was softening the sediment causing the machines to sink into the 48% mud enriched bed. To test whether seeding with a pioneer plant species accelerates salt marsh development, fragments of Salicornia procumbens plants were seeded in half of three compartments. Field observations between November 2018 to September 2020 showed that seeding of Salicornia plant fragments re- sulted in significant differences in vegetation cover and species richness in the first growing season. Mud content showe

Het LNV-onderzoeksprogramma Natuurambitie Grote Wateren (BO-NAGW) werd in 2015 gestart mede uit zorg dat natuuropgaven onvoldoende een plek kregen in het waterbeleid. Het antwoord was de Programmatische Aanpak Grote Wateren (PAGW), waarbij het uitgangspunt was om herstel van natuurlijke dynamiek in harmonie te brengen met economisch medegebruik. Wat kunnen we leren van de resultaten van dit programma voor toekomstig onderzoek?

In de afgelopen eeuw is er flink gesleuteld aan de Nederlandse Rijkswateren. De rivierlopen zijn aangepast om het water zo snel mogelijk naar zee af te voeren, een deel van de voormalige Zuiderzee is ingepolderd en in de mondingen van de IJssel, Rijn en Maas is de invloed van de zee teruggedrongen. Alleen de Schelde, de Nieuwe Waterweg en de Eems staan nog in directe verbinding met de zee. De dynamiek in het systeem is daarmee afgenomen. Er zijn en worden allerlei maatregelen genomen in het waterbeheer, gericht op de verbetering van de waterkwaliteit, waterveiligheid, zoetwatervoorziening en natuurwaarden.

Salt marshes form natural barriers between the sea and the land and they provide numerous ecosystem services. In this thesis, we studied the establishment of pioneer vegetation at the edge of the salt marsh. The transition zone from salt marsh to intertidal flat contains diverse and harsh conditions like frequent inundation with salt water, waves, massive temperature variations and a dynamic sediment layer. Annually, plants have to establish is this zone to maintain the salt marsh surface area. Establishment of these plants is affected by tiny worms that crawl around in the soil, dislodging the roots of pioneer plants but also influencing the distribution of seeds in the soil. Additionally, tidal patterns and weather conditions impact the start and length of the growing season, which can influence recruitment success (available seeds) for the following year. Lastly, a dynamic bed-level reduces seed retention and hinders the establishment of plants in spring. The limited availability of seeds in spring was found to be a major constraint for marsh expansion., Kwelders zorgen voor positieve effecten op lokale biodiversiteit, natuurlijke kustbescherming en vele andere ecosysteemdiensten zoals het vastleggen van CO2 en water-zuivering. De toekomst van kwelders wereldwijd ligt onder druk door klimaatverandering en zeespiegelstijging die verslechtering van kwaliteit of erosie kunnen veroorzaken. Op veel plekken kunnen de kwelders niet richting het binnenland migreren door de aanwezigheid van dijken. Wanneer er genoeg sediment beschikbaar is in de waterkolom, is het waarschijnlijk dat kwelders mee omhoog groeien met de stijging van de zeespiegel, mits dit niet te snel plaatsvindt. Ook is de vestiging van vegetatie aan de rand van kwelder essentieel op de kwelder vitaal en veerkrachtig te houden. Het doel van dit proefschrift was om de ecologische en fysische processen die vestiging van pioniersvegetatie aan de kwelderrand beïnvloeden beter te begrijpen.

Salt marshes, providing numerous ecosystem services, are degrading worldwide. To effectively aid conservation and restoration efforts, increased knowledge on marsh expansion processes and the initial establishment of pioneer vegetation is essential. In this study, we disentangle environmental drivers that affect the lifecycle of the annual pioneer Salicornia procumbens at the salt marsh edge. We studied the effect of various environmental variables on the start of germination, germination success and mortality before seed-set in a field experiment in the DutchWadden Sea atWesthoek. Our results indicate that temperature and sedimentation inhibited the initiation of germination. Once germination occurred, higher precipitation rates increased germination success. In contrast,sedimentation rates above 0.5 mm day−1 halved germination success through burial of freshly sprouted seedlings. Unexpectedly, natural germination was low, indicating that seed availability may have been limited, despite a seed source nearby. Frequent inundation, extended periods without inundation (through desiccation of the soil) and a highly dynamic bed level increased mortality beforeseed-set. Consequently, bed-level dynamics (erosion, sedimentation and bed-level variation) impact seed production dually (decrease germination and increase mortality) and thus potentially reproduction success. A high seed reproduction is crucial for annuals, such as S. procumbens, to re-establish the following year. Next to advancing our general knowledge of natural salt marsh expansion, results in this study can also be used to assess the potential of a given site for saltmarsh stimulation or restoration. Seed availability and local bedlevel dynamics are key in the successful establishment of a salt marsh pioneer: Salicornia procumbens.

Salt marshes are vegetated ecosystems between land and sea, hosting unique plant and animal communities, contributing to crucial habitats for birds and providing numerous other ecosystem services. They form a sustainablenature-based coastal protection, and its protective value increases with the width of the system. Salt marshes and their adjoining tidal flats are often studied separately. At present, there is a lack of studies that an array of abiotic and biotic variables that potentially affect successful vegetation establishment.Unfavourable soil conditions may limit establishment as well as bioturbation of infauna. This is related to the marsh expansion potential and could aid in salt marsh restoration and marsh growth stimulation projects. In a naturally developing salt marsh, we sampled the elevation gradient from the tidal flat to the low marsh for abundance of benthos was highest landwards of the transition zone, in the pioneer zone. Distinct meiobenthic groups occurred in the different zones along the tidal flat to low marsh gradient, but macrobenthos was largely absent from the muddy soil. In the sparsely vegetated transition zone, the abundance of salt-marsh seeds was low, similar to the tidal flat. It suggeststhat, even though a seed source was in proximity, seed availability in spring was insufficient to achieve lateral marsh expansion. Clustering and nMDS analyses showed that an identifiable transition zone was lacking. The transition zone resembled the bare tidal flat in terms of its abiotic and biotic conditions. This was mainly driven by significant changes in soil oxygenation and seed availability.

Spatial planning has to deal with trade-offs between various stakeholders wishes and needs as part of planning and management of landscapes, natural resources and/or biodiversity. To make ecosystem services (ES) trade-off research more relevant for spatial planning, we propose an analytical framework, which puts stakeholders, their land-use/management choices, their impact on ES and responses at the centre. Based on 24 cases from around the world, we used this framing to analyse the appearance and diversity of real-world ES trade-offs. They cover a wide range of trade-offs related to ecosystem use, including: land-use change, management regimes, technical versus nature-based solutions, natural resource use, and management of species. The ES trade-offs studied featured a complexity that was far greater than what is often described in the ES literature. Influential users and context setters are at the core of the trade-off decision-making, but most of the impact is felt by non-influential users. Provisioning and cultural ES were the most targeted in the studied trade-offs, but regulating ES were the most impacted. Stakeholders characteristics, such as influence, impact faced, and concerns can partially explain their position and response in relation to trade-offs. Based on the research findings, we formulate recommendations for spatial planning. (c) 2017

Spatial planning has to deal with trade-offs between various stakeholders’ wishes and needs as part of planning and management of landscapes, natural resources and/or biodiversity. To make ecosystem services (ES) trade-off research more relevant for spatial planning, we propose an analytical framework, which puts stakeholders, their land-use/management choices, their impact on ES and responses at the centre. Based on 24 cases from around the world, we used this framing to analyse the appearance and diversity of real-world ES trade-offs. They cover a wide range of trade-offs related to ecosystem use, including: land-use change, management regimes, technical versus nature-based solutions, natural resource use, and management of species. The ES trade-offs studied featured a complexity that was far greater than what is often described in the ES literature. Influential users and context setters are at the core of the trade-off decision-making, but most of the impact is felt by non-influential users. Provisioning and cultural ES were the most targeted in the studied trade-offs, but regulating ES were the most impacted. Stakeholders’ characteristics, such as influence, impact faced, and concerns can partially explain their position and response in relation to trade-offs. Based on the research findings, we formulate recommendations for spatial planning.

De natuur in de grote wateren is mede de verantwoordelijkheid van het ministerie van Economische Zaken (EZ). Onder de vlag van de Rijksnatuurvisie schetst EZ in de Natuurambitie Grote Wateren (NAGW) het perspectief op toekomstbestendige natuur van de grote wateren. De natuurambitie richt zich op de zes grote wateren in Nederland: het rivierengebied, de Zuidwestelijke Delta, het kustgebied, het Waddengebied en het IJsselmeer. Het voorliggende rapport betreft een studie in de Zuidwestelijke Delta (ZWD).

Het Ministerie van Economische Zaken vroeg Wageningen Marine Research om met behulp van de door Deltares opgeleverde modelresultaten inzicht te geven in de bij elk van de zes doorgerekende maatregelrichtingen te verwachten ecologische toestand in 2050.

Foraging distributions are thought to be density-dependent, because animals not only select for a high availability and quality of resources, but also avoid conspecific interference. Since these processes are confounded, their relative importance in shaping foraging distributions remains poorly understood. Here we aimed to rank the contribution of density-dependent and density-independent effects on the spatio-temporal foraging patterns of eurasian oystercatchers. In our intertidal study area, tides caused continuous variation in oystercatcher density, providing an opportunity to disentangle conspecific interference and density-independent interactions with the food landscape. Spatial distributions were quantified using high-resolution individual tracking of foraging activity and location. In a model environment that included a realistic reconstruction of both the tides and the benthic food, we tested a family of behaviour-based optimality models against these tracking data. Density-independent interactions affected spatial distributions much more strongly than conspecific interference, even in an interference-prone species like oystercatchers. Spatial distributions were governed by avoidance of bill injury costs, selection for high interference-free intake rates and a decreasing availability of benthic bivalve prey after their exposure. These density-independent interactions outweighed interference competition in terms of effect size. We suggest that the bottleneck in our mechanistic understanding of foraging distributions may be primarily the role of density-independent prey attributes unrelated to intake rates, like damage costs in the case of oystercatchers foraging on perilous prey. At a landscape scale, above the finest inter-individual distances, effects of conspecific interaction on spatial distributions may have been overemphasised.

De hoeveelheid slib, de weinig geleidelijke land-water/zoet-zout overgangszones en de sterk beïnvloedde hydromorfologie zijn knelpunten voor het voedselaanbod voor vogels en vis, de biodiversiteit en Natura 2000 doelen in de Eems-Dollard. Overheden, bedrijfsleven en natuurorganisaties hebben de handen ineengeslagen om de natuur in het estuarium te verbeteren met kansen voor economisch medegebruik in het programma Eems-Dollard 2050.

Deze memo beschrijft recente inzichten op het terrein van ecologische kantelpunten die zijn opgedaan in onderzoek en bij Rijkswaterstaat. Gegeven de korte projectduur (twee maanden) is er niet gestreefd naar volledigheid, maar zijn er inzichten bijeengebracht die behulpzaam zijn om de discussie aan te zwengelen over wat de kantelpuntentheorie kan betekenen voor het beheer, evaluatie en monitoring van de grote wateren. In het sterk gemodificeerde Nederlandse watersysteem is het moeilijk om vast te stellen of alternatieve evenwichten onder gelijke condities mogelijk zijn en dat kantelpunten hiertussen plaatsvinden. Alternatieve evenwichten en terugkoppelingsmechanismen zijn het best onderbouwd en omschreven in de literatuur voor de Waddenzee en Veluwemeer. In de estuaria zijn er veel indicaties maar ook veel onzekerheden. In het rivierengebied is het de vraag of alternatieve evenwichten kunnen bestaan. Het beter begrijpen van terugkoppelingsmechanismen in de Nederlandse zoete en zoute wateren, en de interacties hiertussen, wordt echter breed onderschreven. Terugkoppelingsmechanismenzijn met het kantelpuntenconcept goed te onderzoeken voor alle watersystemen en een beter begrip hierover is nuttig voor beleidsevaluaties, het inschatten van het effect van ecologische ingrepen en monitoringsplannen. Het is belangrijk om ook rekening te houden met ‘onbekende’ en niet kwantificeerbare factoren die de veerkracht van een ecosysteem kunnen beïnvloeden. Er is nog niet veel bekend over de invloed van microverontreinigingen, trofische cascades (vissen, vogels), microbiële bodemactiviteit en de rol van hydromorfologische dynamiek in rivieren en estuaria op de ecologische veerkracht van een watersysteem. Het is aan te bevelen om eerst met een aantal casestudies teverkennen wat de mogelijkheden en datavereisten zijn om met langjarige tijdreeksen (ecologie, waterkwaliteit) indicatoren te bepalen die iets zeggen over verandering in ecologische veerkracht. Voorts doen wij de aanbevelin