Authors: Tószögyová, Anna; Storch, David;

The Living Planet Index (LPI) measures the overall population trend of vertebrate species during last decades and has been repeatedly used for evaluation of the current state of the biosphere. The Living Planet Report, published by WWF, states, based on the LPI, that vertebrate populations decreased by more than two-thirds since 1970. This is in striking contrast with the studies based on the same population data (Living Planet Database, LPD) which show that in average, increasing and decreasing vertebrate populations (winners and losers) are more or less balanced. We show that the calculation of the LPI is seriously biased by several mathematical and statistical issues which produce asymmetry in weighting decreasing and increasing populations. When these errors are corrected, the recalculated LPI does not show overall significant decline nor increase of vertebrate populations. This does not necessarily mean that the human-made changes in the Anthropocene lead to a perfect balance of winners and losers; instead it may indicate that available data (collected in the LPD) are not sufficient for proper evaluation of the current state of the biosphere.