Costs of scaring grass-eating barnacle geese often outweigh the benefits

At the current population sizes, the practice of scaring geese off pastures in the province of Friesland probably ends up costing more than it saves. Utrecht University ecologist Monique de Jager and colleagues from Wageningen University and Research, the University of Amsterdam, and the Netherlands Institute of Ecology (NIOO-KNAW) conclude this based on a model study, that was conducted as part of the Dutch contribution to European goose management. The results suggest that scaring geese is cost-effective only when there are few geese in the area.

Conflict between farmers and geese

For a long time, geese in Europe did not fare well, but with the implementation of protective measures in 1950, their populations have rebounded. While this stands as a success story for nature conservation, there is a downside: the increased goose numbers means farmers experience reduced yields as geese consume grass that cannot be harvested. Barnacle geese, in particular, cause agricultural damage as their small beaks allow them to graze the grass shorter than other goose species, which hinders the recovery of the grass. In addition, the birds now stay longer in the Netherlands than in the past, which also results in less time for the grass to recover.

It thus makes perfect sense that farmers frequently attempt to chase away visiting barnacle geese. The idea behind this is that the animals move to specially designated rest areas, where they can graze in peace. Currently, farmers only receive compensation for goose-induced damage outside these rest areas after demonstrating their efforts to scare the animals away.

Appraisal costs

The combination of scaring and designating rest areas is now standard practice. However, Monique de Jager and her colleagues questioned whether this is the most effective way to deal with the animals. The appraisal of damage, necessary for farmers to receive proper compensation, costs money. And once geese are driven away from one area, they move to another area, where damages need to be appraised as well, increasing the overall appraisal costs. Scaring geese also involves expenses, although these are often not borne by the farmers or authorities.

Computer model

To gain insights into the most cost-efficient approach for dealing with the grass-eating animals, De Jager created a computer model. The model simulated the situation in Friesland, the region in the Netherlands where the highest number of geese spend the winter. The researchers incorporated variables such as the amount of grass consumed by the geese, the associated reduction in yield, the grass's growth rate, the geese’s behaviour when chased away, the associated energy expenditure for the geese, and the costs of scaring the birds and appraising damage. The model examined outcomes at various population sizes of geese.

What might seem optimal for an individual farmer, is not necessarily optimal for the entire community.

Not scaring is often more effective

The model indicates that although it still makes sense to chase geese when their numbers are relatively low, it is better to just let them graze peacefully, even outside the rest areas, as the population increases. De Jager points out that, despite sounding contradictory, this actually makes sense. After all, chasing the animals away does not only increase the cost of appraising damage. De Jager: "When you chase geese away, they fly off, expending energy. Consequently, they require more food, which they obtain from the neighbours."

The model also reveals the complexity of the situation. De Jager: "Simply doubling the number of geese does not necessarily result in farmers experiencing double the damage, or the costs of scaring them becoming twice as high. This model enabled us to explore various scenarios and comprehend the interplay between different costs and benefits—something impossible to replicate in real-life situations."

Protected

Barnacle geese continue to enjoy protected status. In Friesland in winter, the population of geese reaches approximately 500,000. De Jager: "Given these numbers, and also at larger population sizes, scaring them is not cost-effective. I do understand that individual farmers wants to scare geese from their pastures. However, our study indicates that what might seem optimal for an individual farmer, is not necessarily optimal for the entire community."