WHEN INVASIVE SPECIES REALLY GET COMPLICATED
NEW PASTURES
The BBC published a tantalizing piece on Ascension Island today – full of economic history and resource economics into which to delve. A volcanic rock in the middle of the Atlantic, Ascension was populated by neither man nor mammal (save those most intrepid of mariners and colonizers, rats and mice, who most likely showed up some time in the 17th Century (Hilton & Cuthbert, 2010)) until 1815. At that time the British set up a military (naval) population to claim the island and to contain Napoleon, exiled on St. Helena 700 miles to the southeast. Though in the path of the trade winds, the mostly barren island kept maritime visits short. This late start to rapid ecological change is a familiar tale for remote unpopulated islands (think Galapagos, Hawaii) worldwide, and it sets up interesting conditions for potential analysis: well-documented, small-scale, and managed by a single decision-making entity (the British Navy) for much of its human history.
Treeless, fresh water was scarce – but ‘well managed’ – an interesting research topic in its own right, and almost certainly an important element in the successful land transformation described in the BBC article – though not addressed directly. Charles Darwin, who arrived in 1836 aboard the Beagle, noted about the careful management of the limited water supply: “indeed, the whole island may be compared to a huge ship kept in first-rate order,” (Darwin, 1846: 293) and that the entire population of the island was in the British Navy – and therefore hierarchical management that could also be used to “invest” in landscape transformations with expected long run payoffs to the British, if not to the actual laborers.
To sustain this population, imports of domesticated mammals led to “about six hundred sheep, many goats, a few cows and horses” residing on the “scant pasture” according to Darwin (Darwin et al, 1846: 294). There appear to have been no introductions of (extremely destructive) feral pigs (Hilton & Cuthbert, 2010), however, despite their general ease of care. These new introductions would have put entirely new pressures on the landscape and hydrological cycle. We know how much damage such introductions can do to existing fragile forest systems from Hawaii (Kaiser, 2014)- we must imagine that they could completely thwart water conservation on an island with no forest. The Hawaiian introductions were also under hierarchical (royal) control, but managed for optimal increase via taboos and with free ranging across forests, rather than with British animal husbandry practices for supplementing sustained consumption of a small human population. The singular control of the island may have meant more active management of ecological change – though not necessarily more sustainable outcomes.
RAIN FOLLOWS THE FOREST – in Hawaii and elsewhere.
Darwin’s 1836 visit added to earlier speculation from another key visitor with an eye for natural history – a member of Captain Cook’s 1775 expedition – who noted that if the gorse on “neighboring” St Helena were transferred to Ascension, then both water and additional greening would follow.”(Economist, 2010) This sparked grand plans for holding water to the island with forestation that had never happened “naturally” due to the island’s remoteness.
The plans were implemented – with great success – and Ascension is now a realization of a ‘man-made tropical forest.’
ECOLOGICAL AND ECONOMIC VALUES: MANAGEMENT FOR WHOM AND FOR WHAT?
But it is new, doesn’t have the ecological complexity of a co-evolutionary structure, and any land species that were endemic are disappearing. Introduced mesquite and other scrub species are expanding rapidly – even on steep slopes – no doubt with particular help from any remaining wild goats. The cats introduced to eat the rats, for example, are now a pest in their own right, particularly for avian species. Meanwhile, changes in tastes and preferences, as well as regulations, have meant an end to decimating turtle harvests by ship crews through the 1930s, and a significant recovery of the population. It is possible that lower bird populations are in turn helping the turtle hatchling populations – it’s tough to reach the ocean!
Turtle hatchlings have it rough (Video).
MANAGING POST-MILITARY: A DIFFUSION OF GOALS
Human uses for the island continue to evolve – from hypothetical containment of Napoleon to a base for disrupting illegal slave trade to its current existence today as a mid-Atlantic node for telecommunications and sophisticated geospatial monitoring and safe turtle hatching habitat, the island’s economic value grows, becomes more diverse, and more integrated into its ecological offerings. As Britain won’t let anyone call Ascension their permanent home, and the original ecological conditions are almost certainly impossible to reinstate, who (or what) should be the guiding force for management?
Choices weighing e.g. endemic species, terrestrial and marine species, and water availability should be made in a holistic manner that includes the relative ecological and economic costs – if we can figure out what those are!
These same challenges apply to many other islands that are reinventing their identities and ecologies after military control – Johnston, Bikini, and Kaho’olawe in the Pacific, Vieques in the Caribbean, Novaya Zemlya in the Arctic – to name a few. They apply, in fact, to any ecosystems whose uses are changing or diversifying with changes in users (demands), ecological and economic structure, access, or scarcity – forests, the global climate system, the oceans, etc. At the dawn of this millennium, we are seeing a receding of the intensification of ecological transformation for uni-dimensional military goals (from a garrison to nuclear testing/waste), but are left with tricky management options going forward.
The diffusion of goals for how to use (consumptively and non-consumptively) ecosystems renders it mandatory that we improve measurement and accounting of natural capital to capture the full range of values (Kaiser and Roumasset, 2002; Fenichel and Abbott, 2014), but it also means governance structures must evolve to be able to use any such improved accounts for improved social welfare. Far from pristine, these ‘remote and isolated’ ecosystems provide fascinating templates for how political, economic, and ecological interactions play out over time. Let’s learn from our mistakes wisely!
Map Image credit: https://en.wikipedia.org/wiki/Ascension_Island
Baker Shot Image credit: By United States Department of Defense (either the U.S. Army or the U.S. Navy)derivative work: Victorrocha (talk) – Operation_Crossroads_Baker_(wide).jpg, Public Domain, https://commons.wikimedia.org/w/index.php?curid=6931019
References:
Kaiser, B (2014). “Watershed Conservation in the Long Run,” Ecosystems 17: 698-719
Mereconomics 