The graph has an X-axis with the years 1970 to 2018 and a Y-axis with indices.
The graph shows a trend line for five groups of vertebrates: mammals, birds, reptiles, amphibians and fish.
The trend line starts at 100 in 1970 and drops to 31 in 2016. The decline appears to be leveling off in the last three years; in 2018 the trend is still 31.