Genetically modified mosquitoes could be the solution to Hawaii’s quickly disappearing avian population, including the island’s famous honeycreepers, writes Michael Specter in The New Yorker:
Every four years, thousands of environmentalists gather at the World Conservation Congress to assess the state of the planet, and to consider what might be done to protect it.
The 2016 congress was held in Hawaii, which is fitting, since the state is often referred to as the endangered-species capital of the world. President Barack Obama, who was born in Hawaii, addressed the conference as it began, shortly after signing a proclamation to create the world’s largest ecological preserve. The act will protect an area of the ocean surrounding the Northwestern Hawaiian Islands that is twice the size of Texas.
Nearly ninety percent of the Hawaiian native plants assessed by the International Union for Conservation of Nature (IUCN) are threatened with extinction, and the avian population is quickly disappearing, too – including the island’s famous, melodious, and brightly colored species of honeycreepers. Climate change has played a role, and so have feral cats, invasive rats, and other non-native species.
But mosquitoes, which carry avian malaria, are a principal reason that just forty-two of more than a hundred species of native Hawaiian birds remain.
There were no mosquitoes on the Hawaiian islands until early in the nineteenth century, when they arrived on whaling ships. That meant that native birds had no exposure to the diseases that mosquitoes carry, and therefore no immunity. One way to protect the birds from malaria has been to kill mosquitoes with chemicals. But mosquitoes can breed in less than a teaspoon of water, and can do so nearly anywhere in Hawaii; their eggs are often inaccessible, hidden in rocks, caves, and the hollows of trees. Poison that can kill mosquitoes frequently also kills the plants and animals that surround them.
Science may offer a solution, however. There are now genetic technologies that, at least in theory, are environmentally benign, but could wipe out the mosquitoes that have decimated the birds of Hawaii – and those that endanger human health as well. That has many conservation ecologists tremendously excited.
Any sentence that includes both the words “genetic” and “modify” causes controversy -often, as is the case with bird preservation in Hawaii, even before the facts are discussed. Critics argue that altering genes to save birds could cause extinctions and other unknown effects, and yet this technology may present the first genuine opportunity to protect these vanishing species.
There are essentially three genetic approaches that might save the birds of Hawaii. The first would be to introduce mosquitoes that have been genetically modified to become sterile, or are programmed to die quickly. This technique is not new: I wrote about the technology for this magazine in 2012, when the British company Oxitec, which stands for Oxford Insect Technology, embarked on an attempt in Brazil, among other places, to eliminate Aedes aegypti, the mosquito species that carries the viruses that cause dengue fever, yellow fever, Chikungunya, and Zika. The data from Brazil demonstrated clearly that, after the release of millions of sterile males, the number of mosquitoes capable of transmitting dengue fever fell markedly. (Only females bite; if they mate with sterile males, their eggs will never mature.)
A related approach involves deploying Wolbachia bacteria, which can prevent viruses from entering the salivary glands of mosquitoes. The third approach is by far the most controversial, and the least likely to be used anytime soon: gene-drive technology.
Advanced technologies offer tremendous opportunities and daunting risks. With gene drive, the stakes are particularly high, and we need to discuss them carefully – to decide as an informed society how we want to proceed. That will require caution, collaboration, and plenty of debate.
Perhaps people will conclude in good faith that the price of saving birds from extinction – or saving the hundreds of thousands of children who die from diseases transmitted by mosquito bite each year – is too high, and that the risks are not worth the effort. Or they might conclude that it would be callous not to try. That is a choice that will affect us all, and it should not be left to scientists or journalists or a small coterie of single-minded activists who speak only in the language of fear.