AND OTHER UNUSUAL SPECIES INHABIT HAWAII
February 17, 2013
silversword plant grows only on the top of Haleakala volcano in Maui.
Of the diverse array of plants I saw in the Hawaiian Islands, silverswords
were one of the few native plants living in their natural habitat. Most
species of plants and animals in our southernmost state found a home
there only in the last couple of centuries, and they were introduced
to the islands by people - sometimes intentionally, sometimes unwittingly.
Any species found in Hawaii was once an immigrant or is the descendant
landforms that rose from the sea as volcanoes, the Hawaiian Islands
represent an environmental marvel. Any animal or plant in Hawaii had
to have an ancestor that came from somewhere else, but species that
arrived from a million years up to a few centuries ago can now be considered
native Hawaiian species. The evolutionary process began soon after each
species arrived. At least it did for those that survived long enough
to begin to change. To survive, a species had to adapt to its new environment,
which was undoubtedly different from its mainland origin. The slow but
inexorable evolutionary process took many thousands of years for some
species; for others, the changes occurred over hundreds of thousands
I saw in Haleakala National Park were at an elevation almost two miles
above sea level. Most plants that might compete with them and the animals
that might eat them would find the environment inhospitable at best.
The first silversword plant I saw in the wild brought to mind the image
of a basketball-size hedgehog with long, silver-coated spines. In the
same family as dandelions, silverswords are a fine example of evolution.
Imagine a dandelion or aster adjusting to a terrain of ancient lava
substrate that supports sparse vegetation.
temperatures, arid conditions, constant wind and intense sunlight year
round, and you have the environment to which the silversword adapted.
The closest surviving relative of the Haleakala silversword is the endangered
Mauna Loa silversword, which is found in similar habitat on the neighboring
island of the Big Island (i.e., Hawaii). Cattle, pigs and goats are
among the threats that led to near extinction of silverswords. The National
Park Service no longer lets them eat the rare plants.
arrived on the islands about 1,500 years ago. The Hawaiian Islands have
been shaped by human hands for so long that the mix of endemics and
invaders, both plant and animal, is remarkable. One day, over the span
of just a few minutes, I saw free-living plants and animals from Indonesia,
Madagascar and six continents. I also saw a couple of species that are
considered native to Hawaii. For an ecologist, exploring the natural
history of the Hawaiian Islands might be compared to window-shopping
at a store in which merchandise from Walmart, Tiffany's, Home Depot
and Toys-R-Us is displayed randomly throughout the store. When you turn
a corner, you have no idea what to expect in the next aisle.
species, such as the predatory Indian mongoose, have had significant
impact on the native fauna. The mongoose was introduced to the islands
in the 1880s to protect the sugarcane industry from rats that were eating
into the plantation owners' profits. As with many such introductions,
things didn't go according to plan. The mongoose found it was much easier
to eat native birds and their eggs than to chase rats. These ferret-like
carnivores still slink around on at least three of the larger islands.
green sea turtles and monk seals frequent Hawaiian beaches. Rare Hawaiian
geese walk around the tops of volcanoes where silverswords live. These
species were not introduced by humans and can qualify as extant Hawaiian
natives. Of Hawaii's remaining flora and fauna, probably more than 95
percent are newcomers that have joined this unusual ecosystem in the
last couple of centuries. Collectively, native and immigrant species
make Hawaii a place of wonder for any botanist, zoologist or ecologist
- and a beautiful vacation spot for anyone.
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