So why do so many creatures go extinct? There is always a slow rate of extinction due to random events. The majority of species died during 5 mass extinction events that happened millions of years ago. The most recent event was 65 million years ago when dinosaurs were killed by an asteroid impact. This extinction probably killed 75% of the species that were on the planet. 200 million years ago an extinction event killed 50% of the living creatures and was caused by massive volcanic eruptions that produced toxic dust that blocked sunlight. The largest extinctions event on the planet was 252 million years ago and it caused more than 96% of marine and 70% of terrestrial species to go extinct. It is thought that high CO2 concentrations in the atmosphere caused widespread climate shift and increased ocean acidification enough to completely devastate food webs. The oldest known mass extinction event was 440 million years ago and also saw a huge reduction in species (60%, at that time there were no land species). This extinction event was caused by global cooling and a large-scale sea level drop. Common among all of these mass extinction events is that natural disasters caused a shift in the world’s climate. The species that exist on the planet are adapted to their current climate, species go extinct when climate changes.
So many salmon have been caught and their rivers dammed up that many species are close to extinction. We created the Endangered Species Act (ESA) to protect species that are on the brink of extinction, but this legal mechanism does not fix habitat degradation, the root cause of extinction. For instance we built hundreds of dams in the Pacific Northwest during the 40’s for cheep electricity, to control flooding and for water security. We built way more dams than we needed and now these dams are blocking ancient spawning grounds of endangered salmon. Restoring essential habitat for these fish is critical to avoid their extinction. Many people don’t want to pay to remove dams, they say it is just not worth the money. This type of short sighted outlook will continue our current rapid pace of extinctions, which could be slowed by the restoration of land and ocean habitats.
So now we have caught ourselves in a pickle, we have created a changing climate that is causing mass extinctions! We are at a turning point in our history, if we wish to survive we must maintain ecosystem functions. We need clean air and water for survival, if we want to live on this planet we need the plants and animals that we have now. This life is what makes our planet habitable, makes it beautiful and richly complex. It would be a shame to cause a modern mass extinction that changes life as we know it. We need to actively protect the life on this planet to ensure that humans can continue to survive here.