There is an example of a well known emperor called Emperor Ashoka of the Maurya Dynasty in India who ruled almost all of Indian subcontinent from 262 BCE to 232 BCE.

Mauryan period is one of the well researched and documented period of Indian history. Most of the aspects of Mauryan history are covered and Ashoka's inscriptions are well documented, where his inscriptions have been translated from Prakrit.

Ashoka won a brutal war against Kalinga in 261 BC, but the devastation and suffering caused by the war made him renounce violence and gave up expansionist policy. After that, he started on the path of Dhamma

He believed that the state had a responsibility not just to protect and promote the welfare of its people but also forests, wildlife and environment. He banned hunting of certain species of wild animals, forest and wild life reserves were established and cruelty to domestic and wild animals was prohibited.

Some of his inscriptions which support the aforementioned facts are

2nd rock edict - King Piyadasi, made provision for two types of medical treatment: medical treatment for humans and medical treatment for animals. Wherever medical herbs suitable for humans or animals are not available, I have had them imported and grown. Wherever medical roots or fruits are not available I have had them imported and grown. Along roads I have had wells dug and trees planted for the benefit of humans and animals

7th pillar edict - Beloved-of-the-Gods, King Piyadasi, says: Along roads I have had banyan trees planted so that they can give shade to animals and men, and I have had mango groves planted. At intervals of eight //krosas//, I have had wells dug, rest-houses built, and in various places, I have had watering-places made for the use of animals and men. But these are but minor achievements. Such things to make the people happy have been done by former kings. I have done these things for this purpose, that the people might practice the Dhamma.

5th Pillar edict - Cocks are not to be caponized, husks hiding living beings are not to be burnt and forests are not to be burnt either without reason or to kill creatures. One animal is not to be fed to another. On the three Caturmasis, the three days of Tisa and during the fourteenth and fifteenth of the Uposatha, fish are protected and not to be sold. During these days animals are not to be killed in the elephant reserves or the fish reserves either.

These edicts/inscriptions are well translated and are available in various places in the subcontinent. As you can see these have been written in 1st person. To know more about these inscriptions you can find myriad research articles and almost every book on ancient indian history mentions these. Also you can read this where content of all inscriptions is given here at one place or you'll have to go through multiple sources just for this https://www.cs.colostate.edu/~malaiya/ashoka.html#MINORROCK

So we can see evidently how he planted trees, protected forests,animals, etc and also banned even burning of forests and husks (two big reasons of pollution presently) as a part of his Dhamma policy. Hence people were aware even almost 2200 years ago. There are many other examples too which can be mentioned for the same.