Environmental charity Trees for Cities worked with 35 volunteers in Kennington Park within the borough of Lambeth to assess the size and health of its 480 trees.
This yielded an estimate of the trees' annual monetary value, as well as indicating how much carbon they store over their lifetime, how much carbon dioxide and pollution they remove from the atmosphere and how many litres of rainwater run-off they capture.
But it also found low species diversity in the tree population, with plane, Leyland cypress and holly making up 37% of all trees.
The mostly mature planes made up 58% of the park's tree canopy cover, with one large oriental plane being ascribed the highest individual value of £327,000.
Trees for Cities strategic partnerships coordinator Ellen Osborne said: "If we know the value of the trees that we are losing to old age, we can plan and invest in replacing them.
"We’ve already been putting these results into practice and have used them to inform tree planting within Kennington Park, planting 20 new legacy trees which build upon the history of the trees already in the park."