Humans are capable of unthinkable, amazing things; we can conquer any mountain, build skyscrapers of nearly any height and for any purpose (soon there will be ones with floors that can rotate!), and construct homes upon any surface. We can make any climate comfortable with air conditioning or heaters, and basically anything natural can be put to use for our convenience.

This is troubling to me.

I was reading through my Kaplan CSET (California Subject Examination for Teachers) study guide, and it talked about mass extinctions for the science section of the test. It discussed the catastrophe that killed off 99 percent of planetary life in the Paleozoic era 245 million years ago, as well as the extinction that meant the end of "the Age of the Reptiles" in the Mesozoic era 65 million years ago, practically ridding the Earth of dinosaurs.

There is one more mass extinction that the book discussed: the current one, caused by humans. With such activities as development and deforestation (and possibly global warming?), between 17,000 and 100,000 species go extinct every year, depending on the source of the information. The book estimated that, based on current rates, humans may be responsible for the extinction of 50 percent of the Earth's species by 2100, in 92 years.

I thought about this as I listened to my dad talk about watching a mountain lion play in a lawn sprinkler in my neighbor's yard the other day. It isn't uncommon to spot the creatures around my parent's house, and while I know it would be terrifying to see such a big cat on my lawn and that they can do a lot of harm to humans, I feel terrible about it.

I don't know if this is something that happens a lot in other areas of the country, but it seems like there are several death-defying encounters with wildlife in Northern California, where bears and big cats inhabit and where business and residential development thrives. More and more houses and stores pop up every year, taking over the hillsides and valleys. People managed to build a huge casino in the hills around where I live, where it seems like it would be impossible to build such a large establishment. I think about all the animals and plants that live there.

Sometimes my dad's company has had to halt construction of projects because an endangered plant or species was "in the way." Of course my dad would grumble about it, but I would secretly root for the little yellow flower or the tiny salamander on the sites. It's hard because I know my family's livelihood depends on my father's ability to continue working, tearing up the ground for landscaping.

I always mourn the deaths of mountain lions and other animals when they clash with humanity. I do feel badly for them because they are losing places to go. I know they can kill people - and they have. A little boy was attacked by a black bear the other day... thankfully he walked away with a few scrapes only (and I'm sure mental trauma as well).

Every time I hear about a mountain lion being chased through a neighborhood and up a tree to be shot "for the safety of the people," I'm sad. When people talk about stabbing them in the eyes when they find themselves face to face with them, it's hard for me to be completely happy for them.

If I had to pick sides, it would be hard to know where to go. How are animals supposed to know where they can go without being killed? If they see a person walking along a path in their territory, how are they supposed to keep away? They have hunting instincts, and humans are just moving mammals to them.