Droughts. Population explosions. Salty soils.
These are the problems that many say will cause worldwide food shortages in coming decades.
Two have already visited the San Joaquin Valley, where drought and a rising demand for water are leaving farms with progressively salty soil. A 2009 University of California, Davis, study reported that if salinity increases at the current rate, by 2030 the direct annual costs to Central Valley agricultural communities and farms will range from $1 billion to $1.5 billion.
Finding a solution will be one of the many subjects at this week's Climate-Smart Agriculture Global Science Conference at UC Davis. Hundreds of scientists and policymakers from around the world will convene at Davis from Tuesday through Saturday to grapple with these problems and others, many wrought by climate change.
UC Davis plant biologist Eduardo Blumwald, who will speak at the conference, says he knows what needs to be done further development and use of genetically modified crops, also known as GMOs for genetically modified organisms.
Not every scientist agrees. Some believe other methods offer greater crop yields with less environmental damage. And many people see the need for caution with GMOs, concerned that their effects on humans have not been thoroughly established.
Blumwald is not deterred by the opposition.
"There is no other alternative," he said. "Our population is increasing. We'll be at 9 billion people by 2050, and food security is a big problem."
Feeding 9 billion will take a lot of crops, and feeding those crops will take a lot of water a shrinking resource. The UNESCO World Water Assessment Program recently forecast a 40 percent increase in global freshwater demand and a corresponding 35 percent decrease in per capita supply by the year 2025.
As a plant biologist, Blumwald has worked more than 10 years developing genetically modified crops.
"We're putting genes into plants that make them suffer less and grow with less water and produce significantly," said Blumwald.
He sees it as an almost prosaic endeavor. "We've been doing this kind of thing for thousands of years. So where is the problem?" he said. "I've been a professor since 1987, and since then I have never even read of one case of anyone getting an allergic reaction to a transgenic potato chip."
But GMOs remain a contentious issue. Proposition 37, which would have required mandatory labeling of genetically engineered food in California, lost in a close election in November. But GMO opponents continue to push labeling measures and laws in numerous states. The Whole Foods chain announced earlier this year that it plans to label all food with genetically modified ingredients within five years.
Eric Holt-Giménez who graduated in agricultural development at UC Davis and earned his doctorate in agroecology from UC Santa Cruz, questions the headlong rush to use GMOs.
"The assertion on the part of pro-GMO scientists that because we haven't seen any problems with GMO crops over the last 20 years, that it means there are not any that is just remarkably unscientific," said Holt-Giménez, who is also executive director of Food First, a social and agricultural advocacy group.
"No one has ever done a serious demographic study on GMOs' effect on full populations," he said.
Holt-Giménez said he believes genetically modified crops are no silver bullet solution for salty and thirsty soil or for pest control. "Building resilience into the ecosystem is the only way to address the problem," he said.
That resilience has to do with crop diversity, including tree cover on farms and soil and water conservation as has been applied to many small farms in Central America, he said.
"These farms tripled, and in some cases quadrupled, yields and did so without GMOs," he said.
"GMOs don't produce food for poor people," Holt-Giménez said. "They feed cows and they feed cars, so the track record of ending hunger is not well-established."
But UC Riverside plant biologist Alan McHughen said he has not seen any scientific data to support Holt-Giménez's contentions about farms.
Like Blumwald, McHughen sees genetically modified crops as the only solution to future food shortages, although he has a stronger cautionary streak.
"I'm a big proponent of the judicious use of this technology," McHughen said.
"We have to investigate it it has to be treated with respect," he said. "There will be some products that come through that we don't want to be commercialized, and then there will be others that should be commercialized more rapidly."
Call The Bee's Edward Ortiz, (916) 321-1071. Follow him on Twitter @edwardortiz.