Editor's Note: The invasion, occupation and liberation of Guam had a lasting effect on the island's people, government and institutions. Each week leading up to the 75th anniversary of Guam's liberation, the Pacific Daily News will examine how the events of 1941-1944 continue to affect life today. We'll share stories from survivors, family members and historians. Do you know a person we should profile, or do you have a family story you'd like others to know about? Is there a topic we should address? Share your suggestions with us at news@guampdn.com.

The aftermath of World War II introduced two invasive species now abundant on Guam: the brown tree snake and the tangantångan tree. These species proliferated quickly, and today, have remarkably shifted the island's delicate ecosystem.

In this way, the war shaped the island's very physical landscape, Department of Agriculture biologist Anthony Tornito said.

"As CHamorus were busy rebuilding their lives, their everyday neighbors started to disappear, such as the birds," Tornito said.

You can hear the difference: the tree and the snake have drastically disrupted the island's native bird population. Now, there are few birds left chirping on Guam, Tornito said, a direct result of the invasive species' introduction.

Species from war

The tree was introduced by the military after the war because the land was bare, Tornito said.

"To essentially control erosion," he said. "A lot of agriculture and farmlands were abandoned. Tangantångan was able to repopulate and take over the agricultural lands and essentially make those tangantångan forests or thickets, as we know today."

The tree species is invasive, Tornito said, despite it being considered naturalized now. The tree may make a nice-looking forest, but it is not native forest, which is the priority, he said.

"We would love for Guam to have native forest, that way people can know native plants," he said. "It's just emphasizing knowing the native flora and fauna of the island."

The native flora is crucial for the at-risk bird populations.

"We can't introduce the birds back if we don't have native habitat," Tornito said. "The trees are invasive because they do grow and compete against native flora. Our native birds, potentially when they come back, won't have habitat because they require limestone forests. Tangantångan is not their native source of habitat, perching."

While the tree can't support native bird populations, the brown tree snake directly contributed to the decline in native birds.

"The brown tree snake was the stowaway of World War II," Tornito said. "It started in the southern part of the island, and made its way up north."

EDITORIAL:Invasive species are a threat and must be dealt with: Our View

Carried over with cargo, the snake quickly overtook the island, he said. The snake is a native to northern Australia, Solomon Islands and Papua New Guinea. Compared to Guam, these areas are large land masses that have animals that can naturally control the snakes.

The snake had no natural predators on Guam, with plenty of small animals to eat, including the native birds. With no prior experience with this predator, the prey had no instinctual survival tactics in the face of a rapidly growing snake population.

"It just took a couple to populate the whole island," he said. "It was paradise for the snake."

There is now an estimated two million brown tree snakes on the island.

Fiscal, cultural consequences

The invasive species' introduction carried dire ecological consequences.

The brown tree snake affected ten out of 12 forest bird species on Guam, Tornito said.

The chichirika, egigi and nosa, once native to Guam, no longer exists on island due to the snake.

The chuguangguang, or the Guam flycatcher, no longer exists on island, or anywhere in the world.

"We lost our insect control, we lost our rodent control," Tornito said. "We lost our seed disperses and the pollinators of our forest."

Other species, such as the native ko'ko' bird and sihek, are now critically endangered. There are currently 140 sihek and about 300 ko'ko birds in the world. Both of these birds' natural habitat is the native limestone forest, not the invasive tangantångan tree.

"If you think about the effects of the snakes on science, we weren't really able to study the animals in the wild," Tornito said. "By the time people started to see the effects of the snake on our ecosystem, it was just out of desperation to take in whatever birds we had left and build up a captive breeding population."

MORE:Baited mice dropped in effort to control brown tree snake

The effects extend beyond bird count and science as well, Tornito said.

The snake affects the economy. The image of a snake-infested island is not ideal for tourism, Tornito said. Snakes often caused power outages as well, forcing investments in snake traps around power lines.

"A lot of money is put into controlling and interdicting snakes at the ports of exit," he said. "Every port on Guam, the airport and shipyards, are areas of interest for snake control."

The amount of money invested in population reduction and controlling the ecological harm is grand, Tornito said.

It's about culture too, he said.

"When we lost the birds, we essentially lost part of the culture," Tornito said. "When we lost our birds, we stopped teaching our children what they were. With the chuguangguang being fully extinct, essentially the word became obsolete."

This lack of knowledge has distorted the image of Guam, Tornito said.

MORE:Letter: Customs protects against biosecurity threats, calls on stakeholders for input

"You have the non-native tree that was introduced post-World War 2, and the non-native snake, and they kind of overtook over the years, and essentially they became embedded in people's minds that they're here," he said. "It's the birds that belong here."

We all call Guam home, and with this comes a responsibility, Tornito said.

"We have to prioritize the native flora and fauna, because this is where they're found, some of our native flora and fauna are only found on Guam and no where else in the world," he said. "It's critical that we save these resources."

Invasive species today

Today, a new invasive insect is introduced to Guam every single day, said University of Guam professor Aubrey Moore. Globalization after World War II intensified the introduction of invasive species to the island, and all over the world.

The primary invasive species introduced on Guam in recent years include the coconut rhinoceros beetle and the Asian cycad scale, according to Moore, a member of the Guam Invasive Species Council.

Both of these insects cause extreme harm to the island's most abundant native trees: the fadang, coconut palm and palma brava.

Asian cycad scales are a tiny insect pest discovered on island 2003. They live under a white, waxy scale cover and suck the sap from the trees they attach to. Without treatment, the trees become totally covered with scales and start to die within a year.

The coconut rhinoceros beetle was discovered on Guam in 2007, and has ravaged the island's coconut trees since. The beetles bore into the trees for the sap, ultimately killing the trees.

The war's introduction of the brown tree snake killed the birds, Moore said, and now, continued globalization is killing Guam's iconic trees.

"No where else is that happening," Moore said. "This is an ecological problem, not an agricultural problem."

While controlling the species is crucial, Guam's delicate ecosystem may never fully recover, Moore said. Guam is a small island, which makes it more susceptible to the effects of an invasive species.

"The impacts of the invasive species are worse than people appreciate. Things aren't going to come back the way they were," he said. "The environment has forever changed."