Yes this is true if you live near the coast, the sea provide up to 95% of oxygen.
...but when you live five and half hours from the nearest sea and also 6000ft above sea level like the city of Johannesburg, we need the trees for oxygen, which is the reason why Johannesburg is a densely populated tree city.
The trees absorb carbon dioxide from the atmosphere and release oxygen in exchange.
So very sad, unfortunately there are not enough of us who care.
sure seems like it soetimes