its unfortunate when a lot of the suffering in the natural world is caused by humans 'because humans now have been moving more and more into separation from nature' we have been destroying rain-forests and the creatures within it, we have been logging, mining, plundering resources,we have been over using the land without replenishing it, we have been causing desertification of the planet and killing every last bug with chemicals, we have been polluting the sea and over fishing it causing even more suffering by killing by catch of dolphins and turtles that just get thrown back into the sea because they cannot be sold. Us humans cause so much suffering in the name of profits and greed.
yes some amount of suffering exists like you said, ones health, aging, and the threat of being hurt or even eaten by something else but this was in somewhat a kind of natural balance but what human beings have caused in the last few thousands years is out of balance to the point in the end, it will be us who will have to suffer as this entire world collapses before our eyes.