Fertilizer Leakage to the Marine Environment, Ecosystem Effects and Population Trends of Waterbirds in Denmark

Møller, Anders Pape; Flensted-Jensen, Einar; Laursen, Karsten; Mardal, W.

doi:10.1007/s10021-014-9810-4

Cited by 18 publications

(18 citation statements)

References 35 publications

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“…A higher level of total N in aquatic environments results in high primary productivity as reflected by the concentration of chlorophyll a in the brackish water surrounding Tipperne, and generally in coastal zones (Møller et al. ). Although fertilizers were not used at the nature reserve, large amounts of fertilizer enter Ringkøbing Fjord from Skjern Å, one of the largest rivers in Denmark.…”

Section: Discussionmentioning

confidence: 99%

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Predation and nutrients drive population declines in breeding waders

Møller

Thorup²,

Laursen

2018

Ecological Applications

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Allee effects are defined as a decline in per capita fitness at low population density. We hypothesized that predation reduces population size of breeding waders and thereby the efficiency of predator deterrence, while total nitrogen through its effects on primary and secondary productivity increases population size. Therefore, nest predation could have negative consequences for population size because nest failure generally results in breeding dispersal and hence reduced local population density. To test these predictions, we recorded nest predation in five species of waders for 4,745 nests during 1987-2015 at the nature reserve Tipperne, Denmark. Predation rates were generally negatively related to conspecific and heterospecific population density, but positively related to overall population density of the entire wader community. Nest predation and population density were related to ground water level, management (grazing and mowing), and nutrients. High nest predation with a time lag of one year resulted in low overall breeding population density, while high nutrient levels resulted in higher population density. These two factors accounted for 86% of the variance in population size, presumably due to effects of nest predation on emigration, while nutrient levels increased the level of vegetation cover and the abundance of food in the surrounding brackish water. These findings are consistent with the hypothesis that predation may reduce population density through negative density dependence, while total nitrogen at adjacent shallow water may increase population size. Nest predation rates were reduced by high ground water level in March, grazing by cattle and mowing that affected access to and susceptibility of nests to predators. These effects can be managed to benefit breeding waders.

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Section: Discussionmentioning

confidence: 99%

“…, Galloway and Cowling , Camargo and Alonso , Laursen and Møller , Møller et al. ). Hence, we predicted higher food availability and population density of waders due to immigration from wader habitat with high predation rates and higher reproductive success at fertilized wetland sites due to increased population density.…”

Section: Introductionmentioning

confidence: 99%

Predation and nutrients drive population declines in breeding waders

Møller

Thorup²,

Laursen

2018

Ecological Applications

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“…Fertilizer increases nutrient availability, primary productivity, and subsequent effects on the abundance of animals at higher trophic levels in the marine environment (Phillippart et al., ; Møller et al., ). Mean effect size of fertilizer on waders was only +0.024 (0.033), which was not significantly different from zero.…”

Section: Discussionmentioning

confidence: 99%

“…Young waders have to find their own food, and due to high energy requirements and poor abilities to save energy, they operate within narrow energetic margins, for example, a balance between quantity and quality of food (Schekkerman & Visser, 2001;Maier, 2013). To this array of parameters influencing wader populations, we included change in nutrient load in the environment as a proxy for primary productivity and amount of benthos and thus indirectly carrying capacity for breeding birds (Philippart et al, 2007;Møller, Flensted-Jensen, Laursen, & Mardal, 2015). Thus, nutrient load can be an important parameter, although a straightforward relationship between nutrients and amount of invertebrate food for young cannot be expected (Schekkerman & Beintema, 2007).…”

Section: Introductionmentioning

confidence: 99%

Multiple components of environmental change drive populations of breeding waders in seminatural grasslands

Laursen

Balbontı́n

Thorup³

et al. 2018

Ecology and Evolution

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Environments are rapidly changing due to climate change, land use, intensive agriculture, and the impact of hunting on predator populations. Here, we analyzed long‐term data recorded during 1928–2014 on the size of breeding populations of waders at two large nature reserves in Denmark, Vejlerne and Tipperne, to determine the effects of components of environmental change on breeding populations of waders. Environmental variables and counts of waders were temporally autocorrelated, and we used generalized least square (GLS) by incorporating the first‐order autoregressive correlation structure in the analyses. We attempted to predict the abundance of waders for short‐term trends for two nature reserves (35 years) and for long‐term trends for one nature reserve (86 years), using precipitation, temperature, nutrients, abundance of foxes Vulpes vulpes, area grazed, and number of cattle. There was evidence of impacts of nutrients, climate (long‐term changes in temperature and precipitation), grazing, mowing, and predation on bird populations. We used standard random effects meta‐analyses weighted by (N–3) to quantify these mean effects. There was no significant difference in effect size among species, while mean effect size differed consistently among environmental factors, and the interaction between effect size for species and environmental factors was also significant. Thus, environmental factors affected the different species differently. Mean effect size was the largest at +0.20 for rain, +0.11 for temperature, −0.09 for fox abundance, and −0.03 for number of cattle, while there was no significant mean effect for fertilizer, area grazed, and year. Effect sizes for two short‐term time series from Tipperne and Vejlerne were positively correlated as were effect sizes for short‐term and long‐term time series at Tipperne. This implies that environmental factors had consistent effects across large temporal and spatial scales.

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“…Danish coastal waters support a large population of wintering waterbirds that breed in Scandinavia and use coastal Denmark for moulting (Joensen, , ; Laursen et al ., ). We predicted that increased subsidies of N from terrestrial sources would increase the abundance and the size of blue mussels Mytilus edulis , the primary winter food of eiders, and subsequently increase δ 15 N values in feathers derived from ingestion of blue mussels (Laursen & Møller, ; Møller, Flensted‐Jensen & Mardal, ). We further expected terrestrial N subsidies to increase the body condition of eiders.…”

Section: Introductionmentioning

confidence: 99%

Retrospectively analysing condition in historical samples of birds

2018

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Large amounts of nitrogen are used as fertilizer across the globe annually exceeding 100 million metric tons, with consequences for primary productivity and effects at higher trophic levels. We measured δ15N values in feathers from samples of eiders Somateria mollissima wintering on the Danish coast in 2014‐2016 and a century ago, using museum specimens. Blue mussels Mytilus edulis are filter feeders relying on phytoplankton as food and they constitute the main diet of eiders. Feather δ15N increased by 40% during the past century reflecting increased terrestrial runoff of N through agricultural use of fertilizer, in turn supporting increased primary production in shallow coastal systems. This increase in δ15N was associated with an increase in body mass and longer duration of moult. However, there was a recent decrease in the quality of feathers as reflected by more fault bars and a higher degree of feather wear suggesting that longer duration of moult comes at a cost in terms of poorer feather quality. These findings imply that terrestrial nitrogen subsidies to coastal marine systems from anthropogenic sources has profound effects on species such as the eider as revealed by the effects on body condition and plumage quality and hence the ability to fly and dive.

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Fertilizer Leakage to the Marine Environment, Ecosystem Effects and Population Trends of Waterbirds in Denmark

Cited by 18 publications

References 35 publications

Predation and nutrients drive population declines in breeding waders

Predation and nutrients drive population declines in breeding waders

Multiple components of environmental change drive populations of breeding waders in seminatural grasslands

Retrospectively analysing condition in historical samples of birds

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