We can all too easily lose sight of the centrality of seaweed plays in coastal habitat–even in Northern California, where seaweed washes up regularly in clumps and beds along the shore. But if the bull kelp and other marine plants we find in the sandy beaches of northern California seem otherworldly representatives of a marine world, the contraction of kelp forests across much of the offshore areas where they provided such rich habitats may soon start to reveal how much coastal waters demand to be seen not as so separate from the land, but part of a complex ecotone, a region where land and sea interact and what we see as underwater species impact a large ecosystem that provides atmospheric oxygen, and is integral to coastal biodiversity that gives so much of a specific character to the California coast, and indeed gives us so much of a sense of where we are.
While beached kelp may be present before our eyes, the problems of mapping of kelp forests with any fixity complicates how we process the disappearance of offshore kelp beds in an amazingly rapid timeframe. And the failure of creating an actual image capture registering the extent of kelp forests poses limits our awareness of their diminution off coastal waters. The observations of the shrinking of coastal spread of bull kelp is based on local aerial surveys, over a relatively small span of time, the accelerated roll-back of a once-vital region of biodiversity is both global, and demands to be placed in a long-term historical perspective of the way we have removed the underwater and undersea from our notion of coastal environments and of a biosphere.
What was first registered in the plummeting of abalone, and the wasting disease of sea stars, afflicting stars from Baja to Alaska in 2013, suggest a condensation of a radical change in near-coastal environments of global proportions, paralleled by the arrival of warm waters that are not conducive to kelp growth, even before El Nino, and before the the arrival of purple urchins whose levels stars controlled, as if the result of cascading effects of a tipping point atmospheric change.
The quite sudden growth on the ocean floor of “sea urchin barrens,” where the near coastal waters are cleared of seaweeds and kelp, is a global problem. As global oceans absorb warmth of increased global warming, near-shore environments are particularly susceptible to species changes that create large disequilibria–from the bloom of phytoplankton to the rise of purple sea urchins and the dearth of shellfish–that stand to change coastal oceans. Yet the same creatures are often ones that fall of outside of our maps, even if the presence and scale of massive kelp beds and submerged forests are hard to map. And even if we see a shrinking of the large undersea submerged beds of kelp off coastal California, it is hard to have clear metrics of their shrinking over time or past extent–or of intervening in their reduction, which we seem forced to watch as inland spectators.
Indeed, if the presence of coastal seaweed, and the distinctive kelp forest of California’s coastal ocean seems the distinguishing feature of its rich coastal ecology, the holdfasts of kelp forests that are grazed down by sea urchins and other predators are poorly mapped as solely underwater–they are part of the rich set of biological exchanges between the ecotone of where land meets sea, and ocean life is fed by sediment discharge and polluted by coastal communities, as much as they should be mapped as lying offshore, at a remove from the land. Yet the death of beds of kelp that is occurring globally underwater is cause for global alarm.
For from Norway to Japan to but the decline of natural predators of urchins in California has made a rapid rise of urchins on the seafloor along the coast have contributed to a shrinking of once-abundant kelp forests that produce so much of our global atmospheric oxygen. And these hidden underwater changes seem destined to rewrite our globe, as much as climate change, and threaten to change its habitability. Even as large clumps of seaweed are removed by powerful waves, that deposit piles of offshore forests ripped from holdfasts on beaches in northern California, the narrative of large coastal kelp deposits, their relation to climate change and coastal environment demands to be better mapped, as the transition of kelp to barrens afflicts so much of the coastal waters of the Atlantic and Pacific, at so many different latitudes and across such a variety of local cold water ecologies.
While the decline of kelp forests seems as radical as the clear-cutting of redwoods, it is both far more rapid and far more environmentally disruptive, if far less visible to the human eye.For in recent decades, increasingly warming waters and out of whack ecosystems have led to a massive decline of seaweed, decimated by a rise in the sea urchin population to by 10,000 percent off the California coast over only last five years, shrinking kelp forests that stand to catapult us to a future for which we have no map. The long-term decline in sea otters and sea stars, natural predators of the urchins, have removed constraints on urchin growth, which warming waters has encouraged, reducing a historical abundance of kelp in the near coastal waters across California.
This has perhaps been difficult to register due to the problems of mapping seaweed, and indeed registering kelp forests’ decline. The advance of sea urchin populations that have created barrens in coastal waters stands to disrupt and overturn some of the most abundant ecological niches in the global oceans. How has this happened under our eyes, so close tho shore and lying just undersea? We have few real maps of seaweed or kelp, lurking underwater, rather than above land, and leave out kelp from most of our maps, which largely privilege land. But the abundance of kelp that produce most of the global oxygen supply live in underwater ecotones–sensitive places between land and sea, in-between areas of shallow water, abundant sunlight, and blending of land and sea–an intersection, properly understood, between biomes, on which different biological communities depend.
Looking at the offshore seaweed near Santa Cruz, CA, I wondered if the predominantly passive registration of location–onshore registration of sites remotely by satellites, familiar from the harrowing images of the spread of fires, provided a basis to register our states of emergencies that was spectacularly unsuited to the contraction of coastal kelp, despite the huge advances of mapping techniques, and left us without a map to their contraction, or to register the subtle if radical consequences of kelp loss, and the almost as devastatingly rapid progress of their advance as populations of urchins have mowed down underseas kelp beds. For even as we strike alarms for the the decline of global kelp populations and seaweed forests as a result of the warming of offshore temperatures that place the near offshore regions at special risk of atmospheric warming–
–we lack maps of the place of seaweed and kelp beds in their ecotone, and indeed have no adequate maps of seaweed populations under threat.Continue reading