I'm working in an extremely simple power sistem that works both for those that dedicate themselves to master it and animals who just use it instinctivily.
This is the basic idea: autotrophs (plants + others for narrative flexibility) release energy into the air when creating their food (In the plants case, photosintesis), and heterotroph are able to absorb, store and release that energy.
That energy (I don't have a definitive name for it yet, so for the sake of convenience I'll refer to it as Mana as a placeholder) exists pasively on the air and is absorbed pasively by the heterotrophs (humans, animals, fungui...). The more plants in an area, like a jungle or a forest, the more Mana in the ambience, the less plants in an area, like a desert or a city, the less Mana available. Also, the more beings in an area absorbing Mana the less Mana available for each of them.
Mana is absorbed pasively, but beings can make an active efort to actively absorb the Mana around them to absorb it faster or find alternatives ways to acces to it. How fast one can absorb Mana has to be exerciced, and is mostly like breathing manually but throught your skin.
Mana is stored inside those that absorb it until used, that means that the bigger you are the higher reserve of Mana they can have at a time: An ant would be incapable of storing much Mana, while a Blue Whale would be able to store a ridiculous amount.
Finally, how eficiently the Mana is released depends entirely on their technique and knowledge of how to release it. This is basically just how good someone is at rationing both their reserve of Mana and the one around them.
The Mana can be released in two ways: Trough the body or raw.
Trought the body is how most animals use Mana: It basically overcharges a part or the entire body. One could overcharge their muscles to gain superstrenght, or their eyes to be able to see really far or in a diferent color spectrum, or supercharge their brain to be able to process information so fast that time seems to be going slower, or their blood cells to be able to heal wounds at increeased speed. Is basically what you can already do but more. Though you could also do weird things, like moving your organs around to avoid lethal blows.
Releasing the Mana raw is basically... Just that. Release high amounts of Mana at once, basically the contrary of actively absorbing it. The most basic example would be releasing a beam of energy, or just to create light or heat, or release it to impulse oneself through the air, or to turn something you are holding into basically a bullet by propulsing it. Another common use would be releasing Mana to act as a kind of shield by repelling something coming towards you. Using it this way is way more spectacular and allows people to do things that would normally be imposible for their body, but is also a lot more energy expensive. (Ki from dragonball, it's basically the ki from dragonball)
TLDR: Plants give you power, the more plants the more power. No plants around, no power. If you are big enought you can store power for when there are no plants around. Power can be used to make yourself better or you can throw the power at someone else. If you are smart you will not use all your power at once.