From Friends of the Earth (as this come from a politically neutral group it is unedited):
 
Friends of the Earth's assessment of the environmental policies of the candidates for London mayor
 
 
This
 mayoral election has been a race to the top on environmental issues, 
with candidates vying with each other to show that they have the 
greenest policies to improve Londoners’ lives.
Overall, our assessment shows that whoever is the next mayor,
 Londoners will benefit from 
greener policies than those of central government, which has torn up initiatives, from insulating cold homes to supporting solar energy.
All of the main candidates have signed up to policies including 
protecting the Green Belt, opposing Heathrow, and building high-quality,
 zero-carbon homes.
But on the 
critical issue of air pollution, the 2 frontrunners still need to 
toughen their plans if Londoners are to be protected from one of the biggest threats to our health.
The final scores
We’ve also published a 
full breakdown of how we scored each candidate on each issue [pdf].
Our 10 policy tests
Friends of the Earth asked the main mayoral candidates to tell us where they stood on 
10 key policies  which our supporters ranked as the important tests of whether the next mayor will protect London’s environment.
Our aim has been for the candidates to make clear pledges to implement these policies.
Our analysis
Sian Berry (Green Party) and 
Caroline Pidgeon (Liberal Democrat Party) are the joint
 greenest candidates, with each committing to deliver all of our 10 key policies.
Sadiq Khan (Labour Party) and 
Zac Goldsmith (Conservative Party) are 
almost neck-and-neck on scores with Sadiq inching ahead by half a point.
Sadiq has committed fully to deliver more of the key green policies 
needed to protect the environment and Londoners’ health and economy, 
while Zac falls short in more areas.
All of the main candidates have signed up to strong policy on key 
issues which matter to our supporters, including powering London with 
clean energy, ensuring new homes are built to good standards; and 
protecting our green spaces.
However, Sadiq Khan and Zac Goldsmith still need to tighten their 
policies in some areas, including, crucially, cleaning up London’s dirty
 air.
How did the candidates fare?
Sian Berry has scored a well-earned 10/10, with great policy on every single one of our top issues.
In particular, her air pollution policies are excellent, including a 
pledge to convert the entire bus fleet to electric or hybrid vehicles by
 2020, and to bring London’s air pollution down to legal levels by 2020 
- 5 years earlier than current government plans.
Caroline Pidgeon also scores 10/10, having committed to delivering all of our key policies.
Her cycling policies are particularly good, and she was the first 
candidate to support the London Cycling Campaign’s Sign for Cycling 
policies.
However, on some issues, a little more detail on how she plans to deliver would be welcome.
Sadiq Khan, scoring a respectable 8/10, has some 
very good policies on issues such as renewables, divestment, stopping 
fracking, and reviewing the London Plan in the light of the Paris 
climate agreement.
However, Sadiq’s strong support for a new runway at Gatwick is a significant weak point in his environmental policies.
In addition, his unwillingness so far to tackle cold homes by 
introducing minimum energy efficiency standards in private rented 
housing, and his lack of sufficient commitment to dealing with the air 
pollution which blights Londoners’ lives, have let him down. 
Zac Goldsmith, with 7.4/10, also has some very good 
policies on protecting nature, renewables, and keeping strong energy 
efficiency standards for new-build homes.
We particularly welcomed his recent promise to follow the other main 
candidates in supporting the divestment of the London Pension Fund 
Authority from fossil fuels, although he has not committed - as others 
have - actively to call for its divestment (a difference we think is 
important).
Zac’s promise only to back the purchase of clean buses is potentially
 very strong, but without clarification of the start date for this - 
which we did ask for - we can’t give him extra points for it.
In addition, his unwillingness to come out strongly against any new 
airport capacity in London, and his lack of commitment to strengthening 
the London Plan to ensure the city is a leader in tackling climate 
change, let him down.
Who does Friends of the Earth want to win?
Friends of the Earth is party politically impartial - we do not 
support any candidate. Our aim for the mayoral elections has been to 
ensure that all candidates have strong policies on the environment.
Our scoring reflects our assessment of each candidate’s policies on 
environmental criteria, and does not represent an endorsement of any 
candidate.