Hawaii is home to one of the world’s last dry tropical forests. In their prime, these magnificent ecosystems were bastions of biodiversity. Now, only 10 percent of the state’s original dry forests survive. In Intelligent Tinkering, Robin Cabin, an associate professor of ecology and environmental science at Brevard College and a former restoration ecologist for the U.S. Forest Service, draws on his own experience in doing restoration work in the few remaining Hawai'ian dry forests.
Below is the excerpted first chapter from Intelligent Tinkering, by Robert Cabin. August 2011, Island Press.
I could see the charred remains of the ghost forest from the highway. One mile below me, the dead trees rose from the lava like giant skeletons. There were many reasons not to walk down there: the steep slope, the intense heat, the dark and foreboding lava, the dense swath of neck-high African fountain grass I would have to fight my way through to reach the 200-year-old lava flow that ran down to the ruined trees. More than all of this, I didn't want to go because I'd been in Hawaii long enough to visualize the ecological devastation I would see when I got there. But something I could no longer ignore compelled me to go.
I swung my legs over the guardrail, stepped off the highway, and plunged into a sea of dead grass. A prolonged drought on this side of the island had reduced tens of thousands of acres of formerly lush fountain grass (Pennisetum setaceum) to a brown wasteland. Head down, I trudged toward the lava as if walking against a strong, waist-deep current. Inside the tunnel of grass, the air felt heavy and smelled like rotten hay. The brittle stems scratched at my bare arms and legs; after ten minutes I felt the familiar sting of sweat trickling into my blood.
When I reached the flow, I could feel the heat radiating from the black rock through the thin soles of my shoes and into my blistered feet. I paused to brush the fountain grass debris off my face, gulp down some water, and look around. My eyes followed the meandering route of the lava flow past the burned forest and all the way down to the sparkling ocean some six miles and 2,000 feet below me. Across the channel, seventy miles northwest from where I stood on the island of Hawai'i (the "Big Island"), East Maui's 10,000-foot Haleakal Volcano rose majestically out of the sea, and I could just make out the faint outlines of the islands of Kaho'olawe, L na'i, and Moloka'i floating on the horizon west of Maui.
I shouldered my pack and set off across the lava for the forest. There are two main kinds of lava in Hawai'i: when relatively fluid magma cools, it forms smooth, solid, ropy p hoehoe, while relatively viscous magma forms rough, rubbly, clinker-type 'a'. Even though this was a somewhat treacherous 'a' flow (falling on this type of lava often results in nasty cuts and gashes), the walking here was much easier and faster than within the fountain grass. When I first began working here as a restoration ecologist for the National Tropical Botanical Garden in 1996, I wore expensive, sturdy hiking boots, but after the 'a' destroyed my second pair I gave up on the concept of ankle support and switched to cheap, low-cut sneakers. Eventually I acquired my "'a' legs" and rarely fell except when I let my eyes and mind wander too far from my feet. Fifteen minutes into this hike, when I tripped over a loose piece of lava and nearly stumbled into a jagged ravine, I realized with a jolt that I had been looking at the coast and daydreaming about the ocean. It had been far too long since I'd swum and surfed and snorkeled in those waters.
The lowland, dry, leeward sides of all the main Hawaiian islands were once covered by magnificent forests teeming with strange and beautiful species found nowhere else on Earth. Tens of thousands of brightly colored, fungi-eating snails slithered through the trees and inched their way through the dark underlying leaf litter. Vast flocks of giant flightless geese squawked across the forest understories; dozens of species of finchlike honeycreepers sipped nectar, gobbled insects, and sought shelter from the heat and hungry eagles, hawks, and owls.
Paradoxically, the diversity of Hawai'i's primeval dry forests was probably created and maintained by rivers of red-hot molten lava that destroyed everything in their path as they wound their way down the slopes of the volcanoes and into the sea. Before alien species such as fountain grass reached these islands, the native plant communities apparently did not produce enough understory biomass to carry fires much beyond the lava rivers, so the forests on either side of the flows remained more or less intact. Thus, as each wave of new lava cooled and weathered, it was slowly colonized by the species in the adjacent forests. The result of thousands of years of this dynamic cycle was a mosaic of different-aged forests, with different species assemblages growing sometimes literally side by side.
The Hawaiians loved these forests and often chose to live in or near them. Because of the hot, dry climate, many of the trees grew extremely slowly and produced some of the world's hardest woods, which the Hawaiians fashioned into buildings, tools, weapons, and musical instruments. They also made exquisite multicolored capes and helmets containing hundreds of thousands of bird feathers and strung elaborate leis using vines and sweet-smelling flowers.
The first time I walked through a patch of native dry forest containing a grove of alahe'e trees in full bloom (Psydrax odorata, a member of the Coffee family), I told my native Hawaiian colleague that the light fragrance of these small white flowers seemed to creep mysteriously in and out of my nostrils. He smiled and explained that the Hawaiian word alahe'e literally means "to move through the forest like an octopus."
Today we can only imagine what these complex ecosystems looked like and guess at how they worked. Tragically, more than 90 percent of Hawai'i's original dry forests have been destroyed, and many of their most ecologically important species are actually or functionally extinct. For example, most of the native birds and insects that once performed such critical services as flower pollination and seed scarification and dispersal are now gone. Many of the once dominant and culturally important canopy trees are also extinct or exist in only a few small populations of scattered and senescent individuals.
The demise of Hawai'i's dry forests began soon after the Polynesian discovery of these islands around AD 400. Like indigenous people throughout the tropics, these early Hawaiians cleared and burned the dry coastal forests and converted them into cultivated grasslands, agricultural plantations, and thickly settled villages. In 1778, Captain James Cook became the first white man to reach Hawai'i when he accidentally discovered the archipelago while searching for a northwest passage between England and the Orient. Cook's arrival set in motion a chain of events that dramatically accelerated the scope and intensity of habitat destruction and species extinctions throughout the Hawaiian Islands. While the Polynesians had deliberately brought many new species to Hawai'i in their double-hulled sailing canoes (and some stowaways, such as the Polynesian rat, geckos, skinks, and various weeds), their impact was trivial compared with that of the ecological bombs dropped by the Europeans. Thinking the islands deprived of some of God's most useful and important species, Cook and his successors, with the best of intentions, set free cows, sheep, deer, goats, horses, and pigs. Over time, foreigners from around the world unleashed a veritable Pandora's box of ecological wrecking machines, including two more rat species, mongooses (in an infamously ill-advised attempt to control the rats), mosquitoes, ants, and a diverse collection of noxious weeds such as fountain grass.
During relatively rainy periods, when fountain grass greens up and is in full bloom, large sections of the leeward side of the Big Island can look like a lush midwestern prairie. But inevitably the merciless Kona sunshine returns, and the rains disappear for months on end. All that fountain grass dries up and changes from bright green to sickly brown, and the whole landscape looks as if it had been sprayed with Agent Orange. Then all it takes for the whole region to burst into flame like a barn full of dry hay is for somebody to park a hot car on a clump of fountain grass or throw a cigarette out the window.
In contrast to most Hawaiian species, fountain grass originated in an ecosystem (North African savannas) that regularly burned, and consequently it has had thousands of years to evolve mechanisms to cope with and even exploit large-scale fires. I have watched fountain grass rise up from its ashes like a smiling green phoenix after seemingly devastating wildfires: vigorous new shoots quickly appear within the old, burned clumps; seeds germinate en masse; and the emerging seedlings rapidly establish themselves in the favorable postfire environment of increased light and nutrients and decreased plant competition.
The net result of these fires is more fountain grass and less native dry forest. More grass means that during ensuing droughts there will be even greater fuel loads, which in turn will lead to more frequent and widespread fires. This cycle of alien grass, fire, more alien grass, more fire has proven to be the nail in the coffin for dry forests on the Big Island and throughout the tropics as a whole. The reason we don't hear about campaigns to save tropical dry forests is that there are now virtually no such forests left to save. If we want at least some semblances of this ecosystem to exist in the future, we'll have to deliberately and painstakingly design, plant, grow, and care for them ourselves.
As I approached the dead trees, I was hot and felt frustrated because I had never seen this forest before it burned. Yet, in a bittersweet way, I was also glad I had not, because even with no personal connection to this place, I found the sight of those scorched trees almost unbearably depressing. This had apparently been one of the best native dry forest remnants left in the entire state, but we would never know which species had lived here or even what the canopy tree, shrub, and understory layers had looked like. We would never be able to collect seeds or cuttings from the gnarled old trees, which had thrived here against all odds for hundreds of years but now were on the very edge of extinction. One more irreplaceable piece of the mysterious Hawaiian dry forest ecosystem puzzle was gone forever, leaving behind only some tantalizing clues in the fading memories of the few remaining people who had seen these trees alive.
It was a miracle that this forest had survived to the last decade of the twentieth century. Its continued existence was probably due to its location within a large kpuka-an island of vegetation surrounded by a sea of barren lava. The wide sheets of 'a' that encapsulated it must have served as both a natural firebreak and a physical barrier to the herds of goats and cattle that roam these lands looking for something to eat within the endless fields of unpalatable fountain grass. Nobody knows for sure how fire finally managed to penetrate this kpuka. Perhaps fountain grass's steady colonization of its surrounding lava shield provided enough fuel for the fire to hopscotch its way in. Perhaps the wind simply blew a clump of burning grass into its interior. Or maybe, as some say, the fire was deliberately set by a disgruntled rancher or bored teenagers.
By the time I finally reached the dead trees, I had seen more than enough to satisfy my curiosity and my conscience. There were no new leaves or shoots on the trees, no regenerating native shrubs or vines, no seedlings or seedpods on the ground. Up close, the blackened trunks looked more like tombstones than ghosts. I could tell I was looking at the corpses of several different kinds of tree, but I could not determine with any confidence which species they were. Although such hard, dense wood takes forever to rot in this parched environment, I knew it would not be long before the last tree toppled over and disappeared in the underlying thicket of rank fountain grass.
I wiped the sweat out of my eyes and looked toward the Kohala Mountains, twenty-five miles to the northeast, but all I saw was mile after mile of fountain grass interspersed with more barren, black, bleak lava flows. The view to the southwest was only marginally less discouraging: while there were still a few scattered bands of native trees poking up here and there, I saw new roads going in and new construction projects going up virtually everywhere. The Big Island's famous Kona coastline to the west was a mixture of raw lava, groves of thorny alien kiawe trees (Prosopis pallida, or mesquite), and the kind of high-end resorts that rent private pieces of well-stocked paradise for many thousands of dollars a night. Only a few miles away from the kpuka, I spotted the lush greens and glittering, volcano-motif copper clubhouse of Charles Schwab's new $50 million private golf course: apparently he had not found any of Kona's fifteen existing golf courses quite up to par.
I turned away from the sea and the opulence and looked back upslope at the tiny parcels of native trees lining the highway. The North Kona Dryland Forest Working Group had collectively spent thousands of hours to preserve and restore those forest remnants. We had erected and maintained fences, established perimeter firebreaks, killed and cleared fountain grass and other weeds, poisoned rodents, collected seeds, and propagated and transplanted thousands of native trees, shrubs, and vines. Local groups ranging from elementary school kids to native Hawaiian teenagers to real estate agents had repeatedly donated their time and labor to help with these efforts. Hundreds of people within and beyond the Hawaiian Islands had come to see and study this ecosystem. My own scientific research program had progressed from documenting the demise of these forests to experimenting with promising techniques for restoring them at ever larger spatial scales.
Looking at the fruits of our work from this distance, I felt a wave of optimism sweep over me, and for the first time I truly believed that even this saddest of all the sad Hawaiian ecosystems could be saved. I turned around again and looked at the ruined trees. "We can grow another forest here," I muttered. "We know what to do and how to do it."
As the eminent ecologist, conservationist, and pioneering wilderness advocate Aldo Leopold once observed, those who care about the natural world and are aware of what we have done and are doing to it often live "alone in a world of wounds." Environmentalists are almost always forced to play defense: fighting to maintain and enforce hard-won yet meager environmental regulations, scrambling to halt the construction of the next shopping mall, lobbying to preserve the integrity of our last few crumbs of relatively wild and untrammeled places. Thus, one of the most powerful aspects of ecological restoration is that it offers a rare opportunity to go on the offensive; those who do it usually get to, at least occasionally, enjoy the sweet satisfaction of seeing degraded ecosystems and communities and species reverse course and get better.
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