It’s indisputable that animals are eating our trash, according to oceanographer Peter Davison of the Farallon Institute for Advanced Ecosystem Research, but we don’t know the consequences. The ingested material could end up in the tuna that we eat, or as Davison told Science, plastic in fish “may dissolve back into the water…or for all we know they’re puking or pooping it out, and there’s no long-term damage. We don’t know.”
Unknown consequences are bad. If risk probabilities are known, economic modeling can help assess the relative costs and benefits of proposed solutions. But with truly unknown risks, about the best we can do is debate whether the precautionary principle is relevant.