President Bush’s call yesterday for a dramatic slowdown of green-house-gas emissions reflects growing concern for the consequences of climate change. But what about the consequences of the world’s response?

The fact is, food riots resulting partly from the United States’ alternative energy policies have arrived at our front door. Crowds of hungry demonstrators swarmed the presidential palace in Haiti last week to protest skyrocketing food prices.

In recent years, we’ve heard that climate change could be catastrophic for nature and humanity. But it’s becoming increasingly evident that over the next few decades, climate-change policies could prove even more catastrophic.

Food riots have erupted in Mexico, Morocco, Egypt, Cote d’Ivoire, Guinea, Mauritania, Cameroon, Senegal, Uzbekistan and Yemen. Vietnam, Cambodia, India and Egypt have all placed restrictions on their rice exports to drive down domestic prices. Pakistan has reinstated food rationing, which is also under discussion in Bangladesh and rumored in Sri Lanka.

Supposedly climate-friendly policies in the United States and the European Union — subsidizing the production and consumption of such renewable biofuels as ethanol and biodiesel — have diverted such crops as corn, soybeans and palm oil from food to fuel. This, in turn, has increased prices for food worldwide at a time when the highly populous and newly prosperous East and South Asian countries are demanding more of it.

Together, China and India constitute 40 percent of the world’s population. Not long ago, these countries were on the brink of starvation, but now they’re seeing food demand rise ever higher because of years of near double-digit economic growth rates. Energy — critical for making fertilizers, transporting food and running equipment — is at record prices.

According to World Bank data, by March of this year, grain prices had tripled, fertilizer prices had quintupled and energy prices were up 21/​2‑fold since 2000. Since January of this year alone, food prices have increased a staggering 65 percent.

These food-price spikes threaten to undo one of the world’s signal post-World War II achievements. In the ’50s and ’60s, many feared that famine was inevitable. Instead, we witnessed a vast reduction in chronic hunger, from 37 percent of the developing world’s population in 1970 to 17 percent in 2001 — despite an 83 percent increase in population.

Increased agricultural productivity, trade in food commodities and aid from the developed world resulted in a 75 percent drop in global food prices after 1950, making food available to the bottom-rung billions worldwide. The current bump-up in food prices threatens to reverse these gains.

The conversion of natural habitat land for produce-cultivation purposes had been the single-largest threat to biodiversity worldwide, but over the last half century, the global agricultural footprint has nearly stabilized. Now, this achievement is also in jeopardy.

What the US ethanol subsidies do for corn, the European Union’s biodiesel subsidies do for palm oil. EU policies stoke an artificial demand for biodiesel, leading to the clearance of high-biodiversity forests in Malaysia and Indonesia. In both the European Union and the United States, lands previously set aside for nature conservation are once again coming under the plow to meet subsidized biofuel demand.

Agricultural expansion, in turn, increases pressures on certain animal species and leads to higher releases of carbon, from biomass and soil above and below ground. Fertilizers used to increase agricultural yields also increase nitrogen discharged into waters and emissions of nitrous oxide — a greenhouse gas that heats the atmosphere 300 times more effectively than carbon dioxide.

Thus, even if biofuels produce an energy surplus, they would not necessarily be environmentally sound. Worse, they harm the US economy. Higher energy and food prices reduce consumers’ disposable income more or less equally, meaning they disproportionately affect poorer people. Higher food prices, alternative energy subsidies and greenhouse-gas-emissions controls only make it harder for these people to earn a living or afford better education and health care.

Climate-change remedies can lead to greater poverty, starvation and disease, as well as widespread ecological destruction — some of the very misfortunes that they’re supposed to prevent. In our haste to address global warming, we have yet to think seriously about our policies’ unintended effects.

The results have been disastrous, and they’re only getting more so.