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. Bull kelp and other marine plants on the sandy beaches of northern California seem otherworldly representatives of a removed marine world, but their proximity is revealed in remote mapping that promises to remap the role of seaweed in coastal ecosystems, and offer a picture of the terrifying prospects of ocean warming and climate change.
The relatively recent contraction of kelp forests across much of the offshore where they long provided such dense habitats may soon start to contract in ways never before experienced. The remapping of kelp forests, and the problems of their contraction of treasured habitat, 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. Underwater species impact a large ecosystem that provides atmospheric oxygen, integral to coastal biodiversity that imparts a specific character to the California coast, and a sense of where we are–as well as makes it a destination for countless Pacific pelagic, shorebirds, and insects, as well as shellfish and fish. But the decimation of kelp forests, tied to an absence of predators to urchins, but more broadly to the ocean warming of coastal waters, as well as potentially an unprecedented increase in coastal pollution, makes both the mapping of the shrinking of kelp forests and the deciphering of that shrinking pressing problems of mapping, destined to impact a large variety of ocean and land-dwelling species.
The need for such mapping underscores all of our relation to the vital ecosystem of the shores and coastal ocean–even if we too often bracket it from our daily lives. 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.
We lack any striking maps of their destruction of their delicate habitats, comparable, say, to the devastation of forests by fire, whose growth we can witness, terrifyingly, with each overhead passing of a satellite in the recent forest fires, and whose decimation by loggers in earlier generations we can also map. The tree-loss reduced habitats, but I worry we can barely chart save metaphorically the reduction of kelp beds.
We cannot help, however, but to be reminded by maps showing the loss of seaweed with great rapidity of the rapid advance of the burn perimeters of Yosemite wildfires of 2013, North Bay Fires, or the disastrous Camp Fire of 2018. The rapid pace of the loss of these forested lands seems eerily echoed in the shrinking of coastal beds of kelp along Northern California, and correlates to the advance of warming climes.
If we have developed tools to map the continuity, intensity, and growth of forest fires by satellite and drones, the problem of passively registering the loss of kelp forests, and its relation to the advance of urchin beds, removes a part of coastal environments we are in need of mapping. The scale of maps of the destruction of seaweed beds on the California coast are less rooted in real time, but have advanced in striking fashion over ten years, although the ravages of destruction for now seem to remain undersea. But we are less skilled to communicate their crucial place in offshore environments.
The nutrient-rich cold waters of coastal California provided with its rocky seafloor afford a perfect environment for lush kelp forests, that extend up into British Columbia and Alaska. But as waters are warming, with astounding rapidity, we need to ensure kelp beds are mapped, although many are often off the map, and difficult to register, even as their size has come to be threatened by global warming and climate change, in ways that eerily parallel the loss or threats to irreplaceable forested environments. While the nature of the decline of seaweed is not linked to warming waters directly, the shifting ecosystems that climate change has created have caused a drastic and rapid decline of seaweed’s offshore presence that we have yet to fully map. For the passive registration of kelp beds, traced by GPS or captured through aerial photography, is far less hands-on than examination of their extent would warrant, and low-flying satellites of remote sensing offer few possibilities for accurate mapping of their extent. The rapidity of the disappearance to kelp–and beds whose boundaries are shifting in time with the rapidity of the advance of forest fires on the scale of their destruction–pose problems of global dimensions that are pointing for the immediacy of loss of kelp of over 13,000 species whose biodiversity and creation of oxygen by photosynthesis feeds much of the world drives our own ecosystem.
Even a map of globally threatened areas cannot emphasize properly the extent to which the Pacific coastline provides a site of cold waters, ocean upwelling that provides rich mineral nutrients, and sunlight that makes it an especially abundant site of kelp forests, in a true megaregion of coastal ecology whose catastrophic loss is impossible to imagine. Even a map of kelp’s local abundance fails to map its ecoystemic centrality in adequate ways–ways that the diversity of kelp speciation also fails to capture, despite its clear .scientific value to survey the ocean populations that are most risk.
Miller, Lafferty, Lamy, Kui, Rassweller and Reid (2018)/Royal Society Publishing,
The particular vulnerability of the kelp biomass seems to have grown in unexpected ways not only due to climate warming, but to its particular vulnerability to ocean floor sessile predators like purple sea urchins, who are more likely, it is now believed, to eat phytoplankton and microalgae in the kelp understory, rather than kelp itself: however, the role of urchins in diminishing kelp forests, which themselves feed exclusively on sunlight, the combination of how a lack of upwellings due to climate change diminished urchin food supply and the inhospitable nature of warming waters to kelp forests may increase the vulnerability of kelp in coastal oceans.