Starting 30 years ago, a survey was made of the shells on Spain's Llarga Beach every month for three years. When researchers repeated the count just a few years ago, the number of shells was down by two-thirds (compared) with their former numbers. Urbanization or commercial fishing were the likely culprits, but the area experienced no significant increase in either. It did, however, see a threefold bump in tourism. And the number of shells on the beach (dropped) significantly during times of the heaviest tourism. The study is in the journal PLoS ONE. [Micha？ Kowalewski, Rosa Domènech and Jordi Martinell, Vanishing Clams on an Iberian Beach: Local Consequences and Global Implications of Accelerating Loss of Shells to Tourism]

　　Shells provide homes and (hiding) places for organisms from hermit crabs to algae, contribute to the global carbon balance, and even help prevent beach erosion. If tourists worldwide are taking shells in significant numbers, it could have a major (impact) on beach environments. In other words, sightseers shouldn't seize seashells by the seashore.