[permaculture] nitrogen fixing trees/shrubs that feed livestock
Lawrence F. London, Jr.
lfl at intrex.net
Wed Dec 29 04:48:56 EST 2004
Marimike6 at cs.com wrote:
> The Asian brown tree snake comes to mind.
This is incredible, maybe worth reading:
Reason(s) Why it has Become Established: The brown tree snake has become established on Guam due to the absence of natural population
controls and the abundance of vulnerable prey on the island. For example, introduced lizards are popular food items for young snakes. In the
snake's native range, the presence of more diverse faunas and reduced food availability leads to higher population control. Additionally,
because Guam is such a small, remote island, there are not only limited ways for prey to escape predation, but an inability for predators of
the brown tree snake to enter. Furthermore, the non-seasonal climate of Guam, favorable for animal growth and reproduction, allows the brown
tree snake to reproduce year-round.
Ecological Role: An active nocturnal species, the brown tree snake is most often found in densely foliated arboreal habitats. As a food
generalist, the brown tree snake has been reported to prey upon lizards, introduced and domestic birds, rats, geckos, skinks, and any other
available vertebrates. It can consume meals 70% of its body mass, an unusually large amount for a colubrid snake. Currently, there are up to
12,000 to 15,000 snakes per square mile on Guam. The brown tree snake begins to reproduce around age three and deposits up to twelve eggs
once or twice a year in caves, hollow trees, and other areas protected from drying and overheating. The abandoned eggs hatch about 90 days
later. The only known natural predators of the brown tree snake are pigs and monitor lizards. Before the arrival of the brown tree snake,
the only other snake present on Guam was a tiny blind snake ( Rhamphotyphlopys braminus ). Since the blind snake lives in the soil and feeds
on the eggs and young of termites and ants, it does not compete with the brown tree snake for resources and therefore cannot be an effective
natural population control.
Benefit(s): Perhaps the brown tree snake's only benefits relate to the eradication of introduced species. For example, the voracious
appetite of young snakes has helped to rid Guam of introduced lizards. The loss of avian seed dispersers has also caused declines in the
reproductive rate of introduced shrubs, such as Lantana camara.
Threat(s): The brown tree snake is responsible for an incredible decline in Guam's biodiversity. Over the past two decades, this
arboreal predator has caused the disappearance of nearly all of the native forest birds on Guam, including the extinction of the Guam rail
and the Micronesian kingfisher. Nine of the eleven avifauna species present at the time of the brown tree snake's introduction have since
been extirpated. Of the species that have become extinct, five were endemic at the species or subspecies level.
The abundance of the brown tree snake has also caused far-reaching secondary ecological impacts. The snake is responsible for the
decline of the flying fox, a crucial species for the pollination and seed dispersal of tropical trees. Also, without the presence of
certain avian insectivores, the insect population may experience a population boom and therefore negatively impact local agriculture. The
cultural fabric of the island communities are negatively impacted by the brown tree snake as well. Fruit bats, an important part of
indigenous rituals and celebrations on the Mariana Islands, have shown great declines since the introduction of the brown tree snake. The
lower abundance of bats on the islands have not only limited this cultural practice but encouraged the exploitation of other areas in the
Pacific for bat harvesting.
In addition to these negative biological impacts, the brown tree snake threatens the economy of the island through large-scale
electrical power outages and damages to equipment. Since 1978, over 1200 power outages have occurred as a result of the brown tree snake
crawling onto high voltage electrical lines or entering transformers or residential appliances. Moreover, continuously increasing
populations of the brown tree snake are responsible for predation of farm animals, poultry, and pets, leading to further economic
consequences. These snakes are mildly venomous to humans and their non-fatal bite can cause severe sickness in young children.
Control Level Diagnosis: It is recommended that the brown tree snake receive the "highest priority" diagnosis for control. Further
spread of this invasive species should be prevented. More importantly, the current population should be controlled in an effort to reduce
the risk of further spread and to begin to restore affected ecosystems. The significance of the ecological and economical destruction
caused by the brown tree snake has already prompted legislative action in the United States. The U.S. Code: Title 16, Section 4728 states
that a task force should develop a "comprehensive, environmentally sound program in coordination with regional, territorial, state and local
entities to control the brown tree snake in Guam and other areas where the species is established outside of its historic range."
lfl at intrex.net
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