In last week’s Science, a group of researchers pooled data on marine ecosystems around the world to measure the impact of fisheries on marine birds. They found that once fish and krill populations dipped below 30% of their maximum, bird populations began to suffer. Said a different way: if we want penguins, puffins, terns and kittiwakes, we’re going to have to leave them something to eat.
The study reminds me of Peter Vitousek’s famous piece (BioScience 36:368) on “Human Appropriated Net Primary Productivity” in 1986. He estimated that humans use about 40% of all of the biomass produced by plants in a given year; this claim has been supported and refuted about a dozen times since then. Postel et al. have looked at our appropriation of water as well (estimating that we use over half of the available runoff globally). Since everything needs to eat and drink, it then becomes less surprising that we are witness to such startling losses of biodiversity (well…. perhaps we are more than just “witnessing” it!).
The difference between the “one third for the birds” study and these predecessors is policy relevance: it is probably better to know how much we can take before we do irreparable damage, than to simply know how much we are taking. Let’s see if others can follow suit with biomass, water, and land area.
Happy New Year!