but much of the islands' flora is equally interesting

and it's just as vulnerable to the impact of humans.

Over the last centuries, almost 500 species of plant

have been imported into the Galápagos,

some for agriculture, some for gardens

and some by accident.

Like the wild goats who compete with indigenous tortoises for food,

so these newcomers compete with local plants

for sunlight, soil and water.

Santa Cruz, for example, is home to a unique species of plant

called miconia, which is only found on one other island.

Today, it is under threat from the red quinine tree.

First brought onto the island in the late 1940s,

the red quinine tree is very hardy

and it reproduces so rapidly that there were worries

that it might wipe out the whole of the miconia zone.

Today, the National Park Service are actively engaged in a programme

to eradicate red quinine...

...injecting any seed-bearing trees

with cartridges filled with herbicide.

It's expensive, time-consuming work and there are many trees to kill

but scientists are optimistic that they may eventually eradicate

the most damaging newcomers.