RTFA. "To understand how the richness of the mammal kingdom has changed we need a metric that captures a range of different animals and is comparable over time

RTFA. "To understand how the richness of the mammal kingdom has changed we need a metric that captures a range of different animals and is comparable over time. We could look at their abundance – the number of individuals we have – but this is not ideal. We would be counting every species equally, from a mouse to an elephant and this metric would therefore an ecosystem taken over by the smallest mammals look much richer than one in which bigger mammals roam: if the world’s mouse populations multiplied and multiplied – maybe even to the detriment of other animals – then this abundance metric might suggest that these ecosystems were thriving. Instead, ecologists often use the metric biomass. This means that each animal is measured in tonnes of carbon, the fundamental building block of life.1 Biomass gives us a measure of the total biological productivity of an ecosystem. It also gives more weight to larger animals at higher levels of the ecological ‘pyramid’" https://ourworldindata.org/mammals#the-decline-of-wild-mammals-has-a-long-history https://ourworldindata.org/mammals#the-decline-of-wild-mamma...