Once the forces of entropy have taken hold of the hearts of men, the natural world will begin to suffer as well. We have seen a taste of this in the past, when Europeans, following the Christian paradigm that man is supposed to have 'dominion' over the Earth rather than live in harmony with her, ran amok within the world around them. Entire habitats were wiped out without any thought of replenishing them and animals were slaughtered to the point of extinction simply for sport.
We have come a long way in changing our views towards our responsibility for the Earth and know that conservationism is important for all life on this planet, including ours. We can look at the past and see how bad things can get when people stop caring.
Think of the aurochs: one of the most sacred animals in our faith, represented by the primordial Audhumla who gave sustenance to the first forms of life. This beautiful animal was a staple of ancient European life, which was hunted to extinction after the North had been converted. The last specimen died on display in a zoo. The same fate would have met the American buffalo had attitudes towards our treatment of the land and its fauna not changed.
Once the force of nature begin their upheaval, as we have seen, the sun and moon will disappear, earthquakes will ravage the grounds and mountains, and all the fetters that hold the powers of Chaos will be broken. Eggther will strike his harp to awaken the armies of destruction, and Heimdall will respond with a mighty blast of his Gjallarhorn to call the Gods to arms. The World-Tree will tremble, the seas will churn and writhe, and all of nature will begin to tear itself apart. This is Chaos, a desire to return to the state of Ginnungagap, which is violent, destructive, and terrifying.
"I see fire burning, and the Earth blazing, many shall suffer the loss of life. The sun will become a black one, Earth will sink into the dark sea, Austri's toil [the sky] will split, all the sea will crash on the fells. The stormy sea ascends to heaven itself and flows over the earth, the sky is split; thence come snows and furious winds, for the Gods are doomed, and the end is death." (LXXXII.5)
Now, this does not mean that we should go out and support radical political agendas that mislead people with their notion of "saving the planet." What we are talking about here is conservationism, and this comes with the understanding that our responsibility to the Earth must be coupled with intelligence and reason, not sensationalism and fear. When we allow politics to get in the way of actually protecting natural resources, nothing will ever get done. When the only 'solution' offered for environmental issues is granting extraordinary power to governments, we know that we are being deceived by demagogues.
What we must stop are crimes against nature, such as rampant deforestation, poisoning of waterways, and the displacement and/or elimination of various animal species. If we do not accept our responsibility to our Mother Earth we will end up paying dearly for our failures.
Our ancestors believed that the Gods are the force that protects us from such an upheaval of nature, which is why devotion to them is so important. Consider the episode in our lore when Hadding accidentally killed Odur (who had been transformed into a monster by the Gods), then met Freya, Odur's wife, face to face:
"Whether you tread the fields or set your canvas to the ocean,
the Gods will be hostile to you, and throughout the whole Earth you shall find the elements of nature thwarting all your designs."
She explains to Hadding that he would lose the Gods' protection for committing such a heinous act, for at the time Odur was already married to our Goddess of Love, and was thus a God himself.
Therefore, Hadding's slaying was an act of deicide, which may have been the final straw that led the Gods to pull away from humanity in the Ancient Age. Our lore is simply a representation of the battle for the elements between the forces of convergence and of entropy: the Gods and the Etins.
The Gods protect our society from the Etins, just as their religion (Odinism/Asatru) protects our hearts from the latter's chaotic influence. If we turn away from the Gods and embrace Chaos, they will remove their protection and we will be left to deal with the entropic powers on our own.
If we understand the Gods, pay tribute to them, and follow the law, we will remain within their loving embrace. When we all turn against divinity, against life and nature, and against each other, Ragnarok will be at hand as the universe responds to the urlag or karma of our collective decision.