Spirits, like humans, can be mortal. They have their own reincarnation system. When a person is engaged in urban planning, he sweeps away everything in his path. He's killing nature. So, not a few rivers and other reservoirs died, which "hindered" the buildings. They were just bombarded. And the Spirit of the River died. It was in the otherworld. If the atmosphere of the earth had changed and the river had dried up, then the Spirit of the River would have gone away in peace and been born again somewhere in the ocean or would have risen even higher. But, in view of his high level and the death that overtook him due to the fact that it was tortured and killed, it, overflowing with negative emotions, transforms into a malicious Spirit and in a new image terrorizes people living near. The result of reincarnation does not lie in the nature of the Spirit. The very moment of painful death fixates the Spirit on this state and it is reborn into a being who subsequently feels what the Spirit of the River felt when it died. And it felt a dislike for people.
And there are cases when the river is simply clogged, bottles and other garbage are thrown into it, and sewage is drained into clean waters. Spirits sometimes take revenge for this too. But they don't always do it right away and they don't always take revenge on a particular person. There are cities in which such malicious Spirits live, which were once the Spirits of nature and peacefully coexisted with man. The effects of harmful Spirits can be very different, ranging from constant harm to machinery (damage to plumbing, causing accidents, etc.) and ending with sending troubles and diseases to people living nearby.
People harm Spirits because of their unconsciousness, without realizing it, and spirits, in turn, take revenge on them for this. And so on without end. You always have to pay for your ignorance. So, there are a lot of sick people among those who are engaged in the trade of medicinal herbs. Spirits constantly take revenge on those herbalists who harm them, and send diseases on them. And all because nowadays few people follow the traditions of collecting herbs, according to which, for example, it is forbidden to take all plants. But the desire for profit pushes you to do the wrong thing (if you mow down the whole thyme, then there is a risk that it will not recover and will not grow here).
Unfortunately, the worldview of modern people does not assume that rivers, forests, mountains and valleys are alive. This makes people's behavior irresponsible towards nature.
And now an interesting question: why don't the Spirits declare themselves and say that nature is alive, and it is ready to defend itself from attack? The answer is not so simple. It can be considered in analogy with the answer to the question - why the state never legally recognizes the existence of God. The fact is that if such a concept as God appears in the legal field and it is officially recognized that he is the Creator of everything, then therefore we will be subordinate to him, and not to the state, taxes will also be paid to God, etc.. Also with Spirits and nature, officially recognize them, you will have to ask permission for oil extraction, deforestation, etc. Spirits declare themselves, show themselves, pass knowledge to people and in confirmation of all this there are many eyewitness stories. But, stories are just stories until they are officially Acknowledged.