Seabirds — birds that feed exclusively at sea — have long been considered a barometer for plastic pollution in the world's oceans and seas. Today that barometer indicates unequivocally, in case anyone still had any doubts, that the measure is full to overflowing.

According to a new study published in Proceedings of the National Academy of Sciences, as many as 90 per cent of seabirds worldwide have plastic residues in their gut. The research, conducted by a team of Australian scientists, has painted a more catastrophic picture than previously thought: an earlier estimate had put the proportion of affected birds at 29 per cent.

Birds are particularly attracted to small plastic fragments because they mistake them for fish eggs, of which they are very fond. The plastic often remains in the animals' bodies for some time, releasing toxic substances such as nonylphenol.

According to Denise Hardesty, a researcher at Csiro, Australia's national science agency, and co-author of the study, the problem of plastic materials in the sea is growing. "In the next eleven years we will produce as much plastic as has been produced since the 1950s."

Certain bird species in particular, such as some albatrosses (Diomedeidae) and shearwaters (Calonectris diomedea), appear to be more prone to ingesting plastic fragments. The researchers used computer modelling to examine the feeding habits of seabird populations and the concentrations of debris, in order to identify the areas where the problem is most severe.

Surprisingly, the phenomenon proved to be more serious not where there is the most rubbish — such as the notorious Pacific plastic island — but rather near Australia and New Zealand, where the number of animal species is highest.

"I've found all sorts of things inside the animals," explained Denise Hardesty, "lighters, bottle caps and even toys." This alarming scenario is set to worsen: according to the projections produced by the computer model using the researchers' data, by 2050, 99 per cent of seabirds will have plastic inside them.

Plastic birds for a dying sea. Reversing this trend is also our responsibility: we must drastically reduce plastic consumption and increase recycling.