Q1.
Have you ever wondered how so many things on Earth stay in balance?
Answer
They stay in balance because they are not independent. Land, air, water and living things support and affect one another, so a push in one place is answered by the rest of the system.
Take the chapter's own example and follow it through:
cut down a forest
→ fewer trees releasing water vapour and absorbing carbon dioxide
→ less rainfall and more heat retained
→ bare soil is washed away, air quality drops
→ the animals that lived there lose food and shelter
→ the whole local system shifts, not just the trees
→ fewer trees releasing water vapour and absorbing carbon dioxide
→ less rainfall and more heat retained
→ bare soil is washed away, air quality drops
→ the animals that lived there lose food and shelter
→ the whole local system shifts, not just the trees
The same is true in the other direction, which is why the balance can hold: a growing forest cools the air, holds the soil, feeds groundwater and shelters more species, and each of those makes the forest itself more secure.
Why it happens: Earth works as a single vast system in which the output of one part is the input of another. Nothing is preserved by being protected on its own — it is preserved by the parts around it continuing to do their work. That is why the chapter says life on Earth survives not because of one thing but because everything works together in balance.
Tip: This is also why 'protecting clean air, water, soil, and all forms of life' is described in the chapter as essential rather than merely important. You cannot look after one of the four and let the other three go.