2023-10-25 21:45:16
Weeds settle in places where we don’t want them. Several circumstances cause this to happen. A new study has focused on the role of certain birds in this regard.
Waterfowl play an essential role in the dispersal of seeds of native and exotic plants, as well as weeds, between different agricultural landscapes and between terrestrial and aquatic ecosystems. This can cause environmental and economic impacts that have gone unnoticed until now. These are the conclusions reached by a scientific team led by the Doñana Biological Station (EBD), of the Higher Council for Scientific Research (CSIC) of Spain.
To conduct this research, the team selected the common goose as the study species. This is a species whose population is increasing in northern Europe and which often causes conflicts in agriculture by reducing the yield of cereal and grass crops. During the study, they combined the analysis of fecal samples collected in a total of seven different habitats frequented by these species with GPS tracking of the birds. The objective was to know, in addition to the seed dispersal capacity of these species, the habitats in which they carry out this dispersal as well as the distances and trajectories they cover.
A total of 300 excrements collected in different places in southern Sweden were analyzed. In them, the scientists found a total of 41 different plant species from 19 different families, including the exotic herbicide-resistant species Conyza canadensis. Eleven of these species were weeds, including Chenopodium album and Stellaria media, listed as two of the most problematic species for Swedish agriculture, with documented resistance to herbicides and common in the study areas.
“The networks we have developed based on GPS tagging suggest an important connectivity role for greylag geese in agricultural landscapes, with possible implications for the spread of exotic plants and weeds, and for dispersal across the terrestrial interface. -aquatic”, explains María José Navarro, predoctoral researcher at the EBD and main author of the study. And not just for seed dispersal; These findings also suggest that they could be spreading microbes and invertebrates, as well as nutrients.
Geese in one of the study areas in Sweden. (Photo: María José Navarro)
One hundred thousand seeds dispersed per day in the study area
The results confirm that greylag geese connect agricultural habitats through daily flights, potentially spreading weeds between different crop fields, but they also connect aquatic and terrestrial ecosystems through local or long-distance movements. According to data collected using GPS, the geese moved daily from roosting areas, typically islands, lakes and wetlands, to feeding sites in agricultural fields, covering average distances of seven kilometers per day. The most affected areas were precisely the agricultural areas that were close to aquatic ecosystems, since they were more frequented by geese.
Taking into account the abundance of seeds observed in droppings and the number of geese, approximately 100,000 seeds were dispersed daily by geese in the study area in Sweden, approximately 400 square kilometers. Additionally, GPS-tagged geese also occasionally flew non-stop between the two study areas, separated by 300 kilometers, probably also dispersing seeds between them.
“With this study, we confirm that water birds act as seed dispersers in aquatic and terrestrial ecosystems, allowing plants to reach new habitats through their movements,” says the researcher. Despite its importance, its role in seed dispersal has been little studied compared to the roles of other animal species. This research will help predict how plant species can, thanks to waterfowl, adapt to habitat destruction, changes in land use, climate change, or, alternatively, how exotic species and weeds will spread.
The study is titled “Seed dispersal between aquatic and agricultural habitats by greylag geese”. And it has been published in the academic journal Agriculture, Ecosystems & Environment. (Source: EBD / CSIC)
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