An Ecological Tipping Point A case study: Kelp Forests The sea otter (Enhydra lutris) is a keystone species in the kelp forests of western California. Removal of sea otters caused a population boom of the purple sea urchin (Strongylocentrotus polyacanhus) resulting in the decline of the highly productive kelp forest ecosystem. Voice over: Stephen Gill

The kelp forest ecosystem Macrocystis pyrifera Nereocystis leutkeana Kyle McBurnie

The sea otter (Enhydra lutris) as a keystone species Population - dramatically reduced due to hunting for their dense fur The otters live, feed, rest and reproduce within the kelp forests, and rarely need to come to shore. When the otters population declined due to predation from Orca whales, this set in motion a trophic cascade.

Urchin barrens With the reduction of otter numbers the population of urchins exploded. Sea urchins Strongylocentrotus sp. are capable of deforesting kelp forests at a rate of 30 feet per month.

Impacts & Consequences for biodiversity & ecosystems services Before: Kelp forests are similar to rain forests in that they also absorb & store C02 from the atmosphere. The huge range of forest biodiversity acts as a focal point for eco-tourism, with the forests gone this income is lost. After:

References/Images: Seals/surface & otters2: The Alaska Wildlife Alliance, Anchorage, AK 99520-2022 ,Sea Otters and Kelp Forests, Available at: http://akwildlife.org/wp-content/uploads/2013/02/sea_otters_and_kelp_forests_11-5.pdf Seal/Forest:  Rosenstiel School of Marine & Atmospheric Science, Miami, Fl, USA. Underwater Photography 2013 Winner, Kyle McBurnie, California, Harbor seal (Phoca vitulina) in a kelp forest at Cortes bank, near San Diego, CA. Available at: http://www.rsmas.miami.edu/outreach/underwater-photography/2013-winners/ Kelp/fish: National Marine Sanctuaries, Kelp Forests - a Description. Available at: http://sanctuaries.noaa.gov/visit/ecosystems/kelpdesc.html Otter eating: Biodiversity of the Central Coast, Sea otter (Enhydra lutra). Photos by Keith Holmes, Hakai Insitute Available at: http://www.centralcoastbiodiversity.org/sea-otter-bull-enhydra-lutris.html Otter collecting: Arkive.org, Sea otter collecting sea urchin photo by Jeff Foot. Available at: http://www.arkive.org/sea- otter/enhydra-lutris/image-G24397.html Urchin barren, Urchin cover: California Department of Fish and Wildlife, “Perfect Storm” Decimates Northern California Kelp Forests, Photos by A. Maguire & A. Weltz Available at: https://cdfwmarine.wordpress.com/2016/03/30/perfect-storm- decimates-kelp/ Consequences before & after: Natural History Photography Blog, The Disappearing Kelp Forests of San Clemente, Photos by Phillip Cotta. Available at: http://www.oceanlight.com/log/category/photography/aerial-photography Narration by Stephen Gill