you're telling me…'I own the land, but I don't own the trees?'…
That is a very good objection and it goes right to the heart of the matter. You don't 'own' the land. The city government gives you title to it. If the government disappears, so does your 'ownership'.
The only way you would 'own' the land would be if there was no government and you had the largest private army around. Then someone with a larger private army could kick you off and 'own' the land.
The city has the largest army, the police and military, who protect your title. It is a deal. You support the government, they protect you. The government protects your land from trespass by your fellow citizens but not from trespass by itself. If it concludes the public welfare would be overwhelmingly served by some public use of some or all of your land, say for a new highway, it will withdraw your title, subject to no choice by yourself.
The government can accompany your title with restrictions they impose for the public good. You can't make too much noise, can't grow marijuana, etc., restrictions imposed on your use of the land you hold title to. This is called 'zoning'. It is normal.
In Baguio, the economic foundation of the city is tourism. The large, old trees are necessary for tourism. The large trees are NECESSARY for the livelihood of the people of Baguio. The government sees this very clearly and you are zoned to preserve them, for the public welfare.
The government is careful about over zoning. Too many restrictions and it loses your support, you become a revolutionary. So only when something is obviously and overwhelmingly necessary for the public good does it get zoned. The trees fit this description.
Owners joke.."You own the land, but you don't own the trees!". But natural resources have always been excluded from your title. If on your land is a water spring that supplies Baguio, you can't stop it up. "You own the land, but you don't own the spring." The people of Baguio need to use that water for drinking. If a navigable river traverses the land you hold title to, you must allow navigation on that river. . "You own the land, but you don't own the river." The people of Baguio need to use that river for navigation.
For Baguio, the trees are almost as important as the spring would be and certainly more important than river navigation, so they fall legitimately in the things you don't hold title to. The people of Baguio need to use those trees for tourism.

Sincerely,

Tom Ewing