The mayor launched his climate change strategy at the Thames Barrier
Londoners must use less water and plant more trees to prevent climate change from damaging the quality of life in the capital, the mayor has said.
Boris Johnson said measures were needed to combat the danger of increased flooding, droughts and heatwaves.
They included more water metering, more green spaces to "cool" the city and steps to reduce leaks from water mains.
Green Party London Assembly member Jenny Jones said the measures contained "nothing new" and were "inadequate".
Climate change could "seriously threaten our quality of life - particularly that of the most vulnerable people", Mr Johnson said.
Some 1.25 million people are at risk of flooding, along with almost half a million properties, 441 schools, 75 London Underground and DLR stations and 10 hospitals, the mayor said.
The Thames region has lower water availability per person than Morocco yet Londoners consume on average 18 litres per day more than the national average, the mayor said.
Meanwhile 600 million litres of water per day are lost through leaks, he added.
The August 2003 heatwave killed at least 600 people in the city, according to the mayor.
"We need to concentrate efforts to slash carbon emissions and become more energy efficient in order to prevent dangerous climate change," Mr Johnson said.
"But we also need to prepare for how our climate is expected to change in the future."
The mayor also pledged to reduce leakage from water mains, adapt buildings to minimise the need for cooling facilities and improve flood risk management.
Ms Jones said all those suggestions would help combat climate change but said they could have been announced "at any time over the past 10 years".
"These are all good measures, we have got to do all these things," she said.
"But where are the big new ideas? We need the mayor to find ways to reduce our dependence on oil, for example."
She added: "If the mayor ignores the contribution transport makes to climate change, he is ignoring a major part of the problem."