If you're a world leader fishing for ideas then you could try using regulatory bodies, alternatives incentives, and monetary policies to do the following: disincentivising plastic import/manufacturing, disincentivising meat consumption, disincentivising car ownership/road-expansion, disincentivising pets, disincentivising power consumption and fossil fuels, and finally funding education and promoting smaller families with less children (these last two things are intrinsically linked). You also have to come to an agreement to do all of these things alongside other nations, because if your nation stops producing as many cows and pigs then some impoverished nation will just crank up their own production to fill the market gap.
Basically, we would only use a third as much agricultural land to live on if we didn't eat meat. With less people that would use even less land with an added bonus of lower emissions by a massive amount per person in developed nation because of lower fuel cost and power consumption. You can lower emissions even more by investing heavily into more efficient modes of transport like railways and buses, in many cases making towns and cities as well as large distance travel doable on foot without a car. We know that educated people, particularly women, lead to lower population growth: which is a good thing, because less emissions and more efficiency. Basically two techniques are being deployed in this example: lower emissions per person and lower number of persons.
Will this fix the damage we've done to the atmosphere and the planet? No, more complex solutions would need to be employed for individual problems like atmospheric methane to ensure our planet continues to be livable for the next century, but we know for a fact that even slightly lowered human activity has a huge beneficial impact because we saw those beneficial effects firsthand during the pandemic.
But wtf do I know, I'm a banjo. You're a world leader. Visit some Universities, talk to experts on panels, and figure it out.