My emotional response to “The Wipeout Gene,” in which Bijal P. Trivedi describes the use of genetic modification to destroy the mosquito species Aedes aegypti, was trepidation. We see A. aegypti as the vector of human diseases, but the global ecological significance of the species is unknown.
Also disturbing is the implication that assent obtained during a town hall or village meeting of lay individuals was meaningful when substantive understanding of arthropod gene manipulation and its ecological impact is limited among scientists.
It is arrogant, reckless and hazardous to make value judgments on the significance of a species.
Charles F. Lovell, Jr.
Past member, National Vaccine Advisory Committee
In addressing future food supplies and environmental degradation, Jonathan A. Foley’s “Can We Feed the World and Sustain the Planet?” doesn’t mention the elephant in the room: agricultural output has dramatically increased but so has population.
Until the countries that can help provide the means, at affordable prices, to enable people to control their family sizes as many want to do but can’t, humanity is chasing its tail.
Les G. Thompson
Foley could have missed a viable answer to world hunger that would also help mitigate climate change: insects as human and other animal food. Most insects produce very little methane for high-quality protein.
The United Nations Food and Agriculture Organization is mounting an effort to address insects as human food and is planning a world conference for 2013. Academics who refuse to think out of the box and address entomophagy as a valid partial answer to world hunger ignore a useful, productive and highly nutritious solution.
Robert Eller Diggs
Foley’s article overlooked food from the sea. Properly designed fish farms can provide a healthy and plentiful supply of food by using our natural resources more efficiently.
Tel Aviv, Israel
In “Digging Mars,” Peter H. Smith’s overview of the science of exploring the Red Planet, the evidence seems to indicate significant variation in the Martian climate. Earth also has wide swings in climate that are thought to be caused by variations in its orbit. Serbian geophysicist Milutin Milankovic´ identified three of these: orbit eccentricity, axial precession and tilt. Has Smith considered whether or not Mars also has these so-called Milankovitch cycles?
Jerry L. Lundry
In discussing the Phoenix mission, Smith indicates the spacecraft traveled 600 million kilometers to Mars and estimates “the light travel time to Earth” as “about 15 minutes.” But at 186,00 miles per second (about 18 million kilometers per minute), light would need about 33 minutes to make the trip from Mars to Earth.
Boynton Beach, Fla.
SMITH REPLIES: Regarding Lundry’s question, Milankovitch cycles influence the climate on Mars even more than on Earth. Not only does the axis precess (every 51,000 years), but the proximity of Jupiter offers a strong gravitational forcing function that modifies the eccentricity of its orbit and the obliquity (tilt) of the spin axis. As the obliquity wanders with large, chaotic variations (cycles can be several million years), the climate is strongly affected to the point where, during large tilts, the polar ice caps can migrate toward the equator, forming large glaciers on the tall volcanoes.