Image source, Getty Images

Ecologists say 23 bee and wasp species are extinct in the UK, but experts believe there are things that can be done on both a national scale and by individuals to protect the ones which are left.

And you don't need a garden to do it. Find out what you can do here.

Reality Check

Labour leader Jeremy Corbyn said: "We have the lowest level of tree cover of almost any country in Europe."

That's right - 13% of the UK is covered by trees. One country in Europe with a lower level is Ireland at 11%.

Malta has almost no tree coverage

The EU average is more than 30%.

You can read more about the parties' tree-planting proposals here.

The leaders are asked about biodiversity, woodland and nature.

Plaid Cymru leader Adam Price says the "nature crisis" is "critically important" and there needs to be a "legal obligation" on the extinction crisis because we are "facing the mass extinction of a million species."

Green Party co-leader Sian Berry says: "We’re very, very behind on biodiversity and nature."

She says the UK has to "think more carefully" and highlight projects like HS2 which is "going through woodland".

SNP leader Nicola Sturgeon says her party has increased funding for peatland restoration in Scotland and "in terms of tree planting, Scotland is absolutely leading the way", adding that 22 million were planted last year.

Labour leader Jeremy Corbyn is quizzed on his plan to plant two billion new trees in England by 2040 if his party wins the general election.

"Yes that tree planting will take place in national parks," he says. "We will pay farmers to plant trees, we will also be planting in new forest. We have to restore the level of biodiversity in this country."

Liberal Democrat leader Jo Swinson says there needs to be "strict nature targets" to "protect our amazing wildlife and biodiversity."

Her party wants a "new office of environmental protection," she says, adding: "We do need to plant those trees."

Reality Check

Jeremy Corbyn says that "Just 100 companies are responsible for 70% of emissions."

This claim features in a report by the Carbon Disclosure Project from 2017, external. This report looks at industrial carbon dioxide emissions only, and not global warming caused by agriculture use or deforestation.

It also only looks at which companies produce the fossil fuels - unsurprisingly they are mostly oil and gas companies. It doesn't look at the end users such as airlines, or indeed consumers.

Image source, Kirsty O'Connor/PA Wire

The leaders are now discussing renewable energy.

Lib Dem leader Jo Swinson and Plaid's Adam Price agree there's some "positive" news surrounding this topic. Ms Swinson points out that the UK is now "a world-leader in offshore wind".

Meanwhile, SNP leader Nicola Sturgeon - who wants to ensure by 2024 that all new homes use renewable or low carbon heat - pushes Labour's Jeremy Corbyn for his views on nuclear energy.

Mr Corbyn says he wants to move towards a National Grid that has "80 to 90%" of renewable energy - but he won't commit to moving away from nuclear as a source of energy.

He says: "There has to be a baseline of production of electricity from a totally sustainable source."

We didn't catch the Green Party co-leader Sian Berry's thoughts on this issue, as the debate is moving on so quickly. But her party's manifesto pledges to make wind provide about 70% of the UK’s electricity by 2030, with other renewable energies to provide most of the rest.

The Greens also want to ban the construction of nuclear power stations and fracking for gas and oil.

Reality Check

Green Party co-leader Sian Berry said reducing the amount of flying: "does mean targeting those 15% of people who take 70% of all flights".

That figure is based on analysis by a group calling for a frequent flyer levy of a government survey, external carried out in 2014.

It found that 52% of people had taken no flights in the past year, 22% had taken one, 11% had taken two and 15% had taken three or more.

The published figures do not break down far enough to confirm the claim, but researchers from Full Fact , externalspoke to the Department for Transport, which confirmed that a more detailed breakdown of responses suggests that those 15% of flyers made 70% of the total flights.

Image source, PA Media

The leaders are asked about energy efficient homes and how they will persuade people to change their heating systems.

Lib Dem leader Jo Swinson says she wants to retro-fit homes to "insulate properly", saying it will cut people’s bills and will help people save money.

Labour leader Jeremy Corbyn says there will be an investment in zero carbon homes and the retro-fitting of insulation of those homes under his party's government.

Green Party co-leader Sian Berry says "each successive government we've had has neglected this" and "we have a massive backlog" of homes to insulate.

She says the party's plan to invest £100bn a year in climate action will help and £38bn will need to go into homes.

SNP leader Nicola Sturgeon says her party wants to help people insulate her homes and wants non-fossil fuel boilers in homes.

The transition away from fossil fuels "has to accelerate," she says.

Plaid Cymru leader Adam Price says the UK should aim to "meet environmental responsibilities" faster than anyone else.

Aviation contributes about 2% of the world's global carbon emissions, according to the International Air Transport Association (IATA).

We've looked at the differences in emissions from planes, cars and trains in this piece.

Image source, Kirsty O'Connor/PA Wire

The debate has now moved on to how to make transport more green.

Jo Swinson talks about the Lib Dems pledge to stop any more airport expansion. Her party also wants those who fly most to pay more tax.

Sian Berry, for the Greens, says she wants to introduce a Frequent Flyer Levy to reduce the impact of the 15% of people who take 70% of flights.

She adds that the highspeed rail project, HS2, should be scrapped as "that money could be spent so much better".

Nicola Sturgeon says we have to invest more to reduce flights. She says the SNP would aim to decarbonise flights in Scotland by 2040.

Plaid's Adam Price says he'd cancel the third runway as well as pulling HS2: "It's a vanity project," he says.

He also points out that Wales doesn't have any high-speed rail projects and that investment needs to improve to help connect the country.

Jeremy Corbyn is asked about Heathrow's third runway - a key point in any climate change debate.

The Labour leader says he voted against the runway and was keen to invest in the rail network - particularly for trains into Europe - to help reduce the number of short-haul flights.

The BBC's Roger Harrabin says Boris Johnson has been blasted by Friends Of the Earth for ducking the climate debate. CEO Craig Bennett says some of their policies are good - but they lag behind the others. The Tory party would not comment.

Image source, PA Media

The leaders are asked about food and its production.

Green Party co-leader Sian Berry says the UK needs to “plant an awful lot more trees”.

Nicola Sturgeon says we all have to think about the healthy balanced diets "we all have to eat" and "where our food is sourced from".

She says farming practices have to become “more environmentally friendly” and “we should be supporting our farmers to do that”.

Last year in Scotland 22 million trees were planted, she says.

Plaid Cymru leader Adam Price says: “We need to be buying more locally, more local food systems and stop importing it to the level we do.”

Labour leader Jeremy Corbyn says: “We have to look at the balance of our food sources as well.

“And look at the damage we do by flying in vegetables from other parts of the world.”

The first question to these leaders is about the Tory Party's pledge to make the UK carbon neutral by 2050 - and what their party has to offer in comparison.

Plaid's Adam Price lays out his pledge for Wales to be a carbon neutral and single-use plastic free nation by 2030.

Jo Swinson is accused by the presenter of being "less ambitious" because the Lib Dems aim for 2045 for carbon neutrality.

She brings things back to Brexit, saying that it'll be easier to tackle climate change if we're part of the EU.

Sian Berry says a 2050 target welcomes "climate chaos". Her Green Party wants to make Britain carbon neutral by 2030

Jeremy Corbyn is accused of "weakening" Labour's pledge for net-zero energy emissions by the "2030s", which he denies.

Meanwhile, Nicola Sturgeon says rather than "squabbling", everyone should come together to "lead the world" and put pressure on other countries.

The SNP calls for net zero carbon emissions no later than 2040 and net zero of all emissions by 2045.

Reality Check

SNP leader Nicola Sturgeon said: "Scotland is already leading the way, we have almost halved our emissions."

That claim was supported by Scottish government statistics, external in 2018, which showed levels in 2016 were 49% below the 1990 baseline, following a 10.3% drop on the previous year.

Much of that year's drop was attributed to the 2016 closure of the Longannet power station.

But the more recent figures , externalshowed that by 2017 emissions were 47% down from 1990.

Image source, PA Media

The Conservative Party has formally complained to the chairman of the Ofcom Election Committee over Channel 4's debate.

The complaint says the party offered senior cabinet minister Michael Gove in Boris Johnson's place, but that Channel 4 "refused to accept this representative, and stated that they intend to 'empty chair' the Conservative Party if the Prime Minister does not attend."

It describes the channel's decision to "represent" the Tories with an ice sculpture as "a significant breach of the Code through such a provocative partisan stunt, which would itself constitute making a political opinion in its own right."

Plaid Cymru leader Adam Price references his one-year-old son in a bid to show how he's committed to improving the planet for future generations.

The last leader to give opening statements is Lib Dem leader Jo Swinson.

She says the climate crisis is "even more important" than Brexit.

She says we have "two paths" - a poisoned planet, or one that's protected for generations.

SNP leader Nicola Sturgeon says tackling climate change "a moral obligation".

"Scotland is leading the way," the Scottish First Minister says.

She says her party wants to set a new legal target net zero on all emissions by 2035 – ahead of the rest of the UK.

Channel 4

Labour leader Jeremy Corbyn says his party will "kickstart a green industrial revolution".

He says there are 100 companies responsible for 70% of emissions.

"It is time for real change," Mr Corbyn says.

Sian Berry, co-leader of the Green Party, starts things off with an opening statement.

She says all of the other parties will make pledges but only the Greens will carry out those promises.

"Do their plans match the scale of the emergency we face, and do your trust them to get this done?" Ms Berry says of the other parties.