Peepal tree (Ficus religiosa) is a sacred tree in Hindu religion with many spiritual significances as well as medicinal and environmental benefits. It is being worshipped for centuries as it denotes different things according to various Vedas. As mentioned in Mahabharata, the story of Savitri, who brought back her husband's life by tying the sacred thread around the Peepal Tree worshipping the Lord of Death, Yamraj and compelled to return her husband's life. Also, according to many Hindu scriptures, roots of the tree represents Brahma, trunk is Vishnu, Shiva the leaves and fruits are all other deities. Every Saturday water is offered to Peepal Tree believing Vishnu along with Laxmi resides on this tree.

Ecologically, Peepal Tree provides ample Oxygen, purifies the surrounding, kills harmful bacteria, control soil erosion, improve soil structure and its fertility, it is also dust and sound absorbent. It is believed that Peepal tree  releases Oxygen during night also due to a special photosynthesis process called Crassulacean Acid Metabolism (CAM). 

It is believed that Kali Yuga started when Lord Krishna died saying- " Among the trees, I am Aswattha.", i.e., Peepal.

It also has Ayurvedic significance since its every parts; leaf, bark, roots and fruits are of utmost importance for various disorders( leaves cure Asthma, milk derived out from leaves helps relieve eye pain, roots and barks for skin treatment). This tree can cure as much as 50 disorders including diarrhoea, epilepsy and gastric troubles.

Spirituality it denotes Cycle of birth and death ( it never sheds its leaves at once  completely, new leaves come up when older fall) and signifies permanent spirituality ( it's believed that it never dies and thus represents our immortal soul). It is considered a sin to cut Peepal tree.

Thus, along with our religion, we may have been loving our nature directly or indirectly. Worshipping trees implies that trees too are a part of the cosmos like us and are serving earth selflessly.

References:

https://blushin.com/spiritual-significance-peepal-tree-according-mythology.html