The Living Planet Index (LPI) is a measure of the state of global biological diversity based on population trends of vertebrate species from around the world. It does this in much the same way that a stock market index tracks the value of a set of shares or a retail price index tracks the cost of a basket of consumer goods.
The Living Planet Database (LPD) currently holds time-series data for nearly 40,000 populations of more than 5,200 mammal, bird, fish, reptile, amphibian and butterfly species from around the world, which are gathered from a variety of sources such as journals, online databases and government reports. Using a method developed by ZSL and WWF, these species population trends are aggregated to produce indices of the state of biodiversity for communication and informing policy. The global dataset, which is continuously expanded, can be disaggregated to measure trends in different thematic areas, including changes in different taxonomic groups, looking at species trends at a national or regional level, identifying how different threats affect populations and providing an insight into how conservation intervention can promote species recoveries. Using machine learning, the index has also been used to show how populations may respond in future to different policy interventions to see what action is needed to bend the curve of biodiversity loss.
In recent years, new research has highlighted the sensitivity of the LPI to extreme declines and increases in populations, prompting discussions about how metrics such as the LPI can capture change in biodiversity without oversimplifying the state of biodiversity or masking underlying important trends. Conversations are also being had about ecological baselines to compare abundance change to, and what the LPI actually measures.
To help with making sense of the index and to highlight current discussions around it, there is more information available on how the LPI works, how to interpret its sensitivity to extreme changes and how it is calculated.