A conference on sustainable cities might not be the first place you'd look for a discussion on humanity's impact on the ocean, but what our seaside cities put in the air and the ground is having an impact on marine life.  

Marcia McNutt, CEO of the Monterrey Aquarium Research Institute in Moss Landing, CA discussed the environmental degradation in our oceans.  Fertilizer that we apply to land runs off into the ocean, causing plant blooms and then decay; this depletes oxygen, kills marine life, and causes dead zones. McNutt made a strong point in citing that many of the world's biggest cities are located along the coast, presenting a direct threat to oceans. 

Our burning of fossil fuels -- which takes place largely in and around cities -- is changing oceanic pH as 50% of the carbon dioxide we produce heads into upper ocean layers.  There, it is converted to carbonic acid, lowering pH, affecting delicate marine life. The very plants that produce atmospheric oxygen are at risk, as the photosynthetic process is pH dependent.  

In fact, half of the oxygen we breathe is supplied by microscopic plants floating on the surface of the ocean.  The ocean's mid water occupies the largest part of Earth's living space. It cycles carbon and other nutrients, and is responsible for much of the biodiversity on Earth. So mucking up the oceans ultimately affects the air we breathe.

McNutt stated that a population 6 billion strong is a fierce threat to the oceans.  Long have we depended on them as a food supply, but recent technological improvements have escalated our impact.  Some fishermen now raise tuna in pens, scooping up delicate life on nearby ocean floors to feed the carnivorous fish.  Technology is also helping us understand our impact. Recent advancements in robotic technology allow us to explore the deep sea and develop an understanding of just how precious and significant it is to the entire ecosystem.  

McNutt concluded by highlighting cities such as New York, Berkeley, and San Jose, which are making strides in reducing their carbon footprints and overall impact on oceanic ecosystems. 

On a personal level, McNutt's presentation got me thinking about my individual contribution to environmental degradation.  I'm thankful that I live in a small box on a rock, not former wetlands, and I don't have a yard to fertilize.  I'm questioning the value of perfectly green lawns and the beef I could consume because both probably benefit from fertilizer.  Thankfully my city of San Francisco has excellent public transportation, and now I have more drive than ever to make good use of it.