It's very likely that the catcus with short spines will die out faster than the cactus with long spines.
Deforestation is one major concern with harvesting wood. There are also all types of organisms that lose their habitats.
Answer:
Imagine studying a cell. That cell has billions of things you can learn about. Now imagine 37.2 trillion cells each a little bit different but still similar. Now imagine that multiplied by all the different people there are on earth. Now then include all the other types of living animals.
That's biology