Scientific American - USA (2022-02)

DISPATCHES FROM THE FRONTIERS OF SCIENCE, TECHNOLOGY AND MEDICINE

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INSIDE

• Fish flock to rub against sharks


• A new camera type can see around—
  and through —obstacles


• Honeybees balance social distancing
  with care when infected


• Genetic mutations bolster plants’
  survival in extreme desert conditions

CONSERVATION

Taking Back

Nature

New Zealand’s audacious

antipredator drive gains ground

A thousand years ago the islands that

today form New Zealand were riotously

wild. Birds, reptiles and invertebrates flour-

ished in lush forests hundreds of miles from

any other landmass. M ̄aori settlers in the

1200s brought Polynesian rats for food, and

together the humans and the rodents began

to shift the ecological balance. Native spe-

cies started to go extinct.

Enter European ships, bearing new carni-

vores: more aggressive rat species, plus

mice, stoats, and others. These ground-

based predators hunted differently from the

falcons and other aerial threats New Zealand

wildlife had evolved with. Native birds that

slept in burrows made easy prey for prowl-

ing mammals. Invasive predator populations

exploded, devastating native wildlife.

But in the past 60 years humans have

intervened to help old New Zealand ecosys-

tems claw their way back. First, a single five-

acre (two-hectare) islet called Maria Island

(Ruapuke in M ̄aori) was declared rat-free by

ecologists in 1964, five years after volunteers

set poisoned bait. It was a special case. The

white-faced storm petrels at risk there were

especially charismatic—they appear to walk

on water—and easily gained public support.

The ample baiting effort also got particularly

lucky with its placement, ecologists say.

Nevertheless, the serendipitous success

kicked off decades of eradication efforts.

Since then, New Zealand ecologists have

cleared island after island of invasive pests.

About two thirds of the country’s smaller

islands are now pest-free, as are 27 fenced

forest fragments on the main islands (which

10 hectares
165 islands

100 hectares
55 islands

1,000 hectares
22 islands

100,000 hectares
1 island

10,000 hectares
7 islands

5 hectares
77 islands

1960 2020

Islands, by area Islands with extant pests (93) Islands cleared of pests (115) Islands never invaded (114)

Source: Zachary T. Carter and James C. Russell/University of Auckland (

data

)

Each line

represents

one island.

Dots stack

if multiple

species were

removed in

the same year.

Dots mark

the year a

species was

removed.

Each dot

represents

one island.