Food security – the ability to obtain and use sufficient amounts of food – is a fundamental human need and one that has been an important topic in global agriculture in recent years as it grapples with the challenge of trying to feed a population that is growing fast while the rate of crop yields and arable land expansion increases have slowed.

The last several decades have seen significant progress in overcoming the obstacles of population growth, food waste, inefficient distribution and ineffective social-safety nets to improve global food security. There are currently about 805 million people, or 11% of the global population who are undernourished, according to the Food and Agriculture Organization of the United Nations, down from about 1.01 billion, or 19%, in 1990-92.

A factor that must now be considered when addressing the topic of feeding the world going forward is climate change.

The U.S. Department of Agriculture (USDA) in December released a study entitled, “Climate Change, Global Food Security, and the U.S. Food System,” which assesses whether progress in global food security can be maintained in the face of a changing climate. It was prepared as part of the United States National Climate Assessment and part of the U.S. President Barack Obama’s Climate Action Plan. USDA led the production of the report on behalf of the 13 Federal Agencies of the U.S. Global Change Research Program. Thirty-one authors and contributors prepared the report, representing 19 federal, academic, nongovernmental and intergovernmental institutions in four countries.

“The past six years have been a success story in terms of global food security,” said U.S. Agriculture Secretary Tom Vilsack. “200 million fewer people are food insecure than they were six years ago. The challenge we now face is whether we can maintain and even accelerate this progress despite the threats from climate change. “

The report, released during the COP-21 Paris Climate Conference, examines not only the well-documented relationship between climate conditions and agriculture production, but also climate’s impact on access to food, its utilization and the overall stability of each. These effects, it said, occur through climate’s influence on global food-system activities, including food processing, packaging, storage, waste, transportation and consumption.

Many scientists believe that since 1750, rapidly growing human-induced emissions of greenhouse gases have caused increases in global average temperatures, changes in precipitation timing and intensity, rising sea levels, and many other changes. At the COP-21, 195 countries signed an agreement which seeks to take actions that will reduce greenhouse gas emissions which many scientists believe will, in turn, slow global warming.

The team that authored the report reviewed a range of scenarios. Under scenarios with continued increases in greenhouse gas emissions, the number of people at risk of undernourishment would increase by as much as 175 million above today’s level by 2080. Scenarios with lower population growth and more robust economic growth coupled with lower greenhouse gas emissions resulted in large reductions in the number of food insecure people compared today.

Here is a look at some of the report’s most important findings.

-Climate change is very likely to affect global, regional, and local food security by disrupting food availability, decreasing access to food, and making utilization more difficult. Climate risks to food security are greatest for poor populations and in tropical regions. Wealthy populations and temperate regions that are not close to limiting thresholds for food availability, access, utilization, or stability are less at risk. Some high latitude regions may actually experience near-term productivity increases due to high adaptive capacity, carbon dioxide fertilization, higher temperatures and precipitation increases. However, damaging outcomes become increasingly likely in all cases from 2050-2100 under higher emissions scenarios.

-The potential for climate change to affect global food security is important for food producers and consumers in the United States. The U.S. appears likely to experience changes in the types and cost of foods available for import. The U.S. is similarly likely to experience increased demand for agricultural exports from regions that experience production difficulties, yet have sufficient wealth to purchase imports. The U.S. is likely to be able to meet increased export demand in the near term. In the longer term and for higher emission scenarios, increased water stress associated with climate change could diminish the export of virtual water (the water that is embodied throughout the entire production process of a traded commodity) in agricultural commodities.

-Agricultural production is affected by temperature increases, changes in the amount, timing and intensity of precipitation, and reduced availability of water in dry areas. Processing, packaging and storage are very likely to be affected by temperature increases that could increase costs and spoilage. Temperature increases could also make utilization more difficult by increasing food-safety risks. Sea-level rise and precipitation changes alter river and lake levels, and extreme heat can impede waterborne, railway and road transportation.

-Effective adaption can reduce food system vulnerability to climate change and reduce detrimental climate change effects on food security, but socio-economic conditions can impede the adoption of technically feasible adaption options. The agricultural sector has a strong record of adapting to changing conditions. There are still opportunities to bring more advanced methods to low-yield agricultural regions, but water and nutrient availability may be limiting in some areas, as is the ability to finance expensive technologies.

-The complexity of the food system within the context of climate change allows for the identification of multiple food security intervention points, which are relevant to decision-makers at every level. The future need for, and cost of, adaption is lower under lower-emissions scenarios. Trade decisions could help to avoid large-scale price shocks and maintain food availability in the face of regional production difficulties such as drought. Improved transportation systems help to reduce food waste and enable participation in agricultural markets. Public and private sector investments in agricultural research and development, coupled with rapid deployment of new techniques, can help to ensure continued innovation in the agricultural sector. Refined storage and packaging techniques and materials could keep foods safer for longer and allow for longer-term food storage where refrigeration is absent and food availability is transient.

Food availability and security

The report notes that climate change influences availability and stability through each food system activity. Climate can also interact with external stressors such as conflict and with the natural resource base such as soils to alter the stability of food supplies. Increased risk can also result from agricultural expansion into less optimal lands in response to climate trends.

According to the report, crop yields have increased globally by about 1.8% per year on average since 2000, while the area of per-capita-cultivated land has decreased by 9% over the same period, leading to an 8% increase in total per-capita cereal production during that time. Yield increases appear to be diminished by up to 2.5% per decade, globally, due to climate change.

It said local production is particularly important in the tropics, where crops’ biophysical thresholds are already closer to their limitations and where higher temperatures are likely to result in diminished yields. In addition to the direct physical effects of temperature and precipitation changes, climate change influences the range and infestation intensity of crop pests and pathogens.

The report also noted that the influence of climate change on which crops are grown where in the world affects the location of storage, processing and packaging facilities as well as that of the underlying transportation infrastructure for moving food from producer to consumers or to trade hubs.

Food access and stability

Food access involves prices (trading), proximity to food (availability), retail outlets (wholesale/retailing), or farmable lands (producing).

The report said that extreme temperatures, heavy rainfall events, drought, sea-level rise, and storm surge can damage road, rail and shipping infrastructure. Climate’s effects upon transportation infrastructure can hinder the movement of food from its place of production to consumers, altering food prices in response to changes in the cost of transportation disrupting the timing and operation of logistical supply systems between producers and distributors.

It also noted that price volatility has risen in recent years due to a combination of factors, including the widespread occurrence of extreme climate events.

Rapid changes already under way in the food retail sector can improve or reduce resilience to climate change, depending on specific adaptive capacities. Adaptation to higher temperatures may be accomplished with increased refrigeration, for example, though that often comes with increased costs.

The adaptive capacity of food access to changes in climate is potentially very high but varies enormously between high-income and low-income countries and individuals, the report said.

Food utilization and stability

Climate has a number of potential and observed effects on food utilization, which include contamination of the food supply, the nutritional composition of food, and a body’s ability to assimilate available nutrients. Climate change affects food safety by influencing vectors of food contamination and levels of toxins in food.

Temperature increases are associated with bacteria-caused illness related to poor food storage and handling practices in the supply chain. Fungal contamination resulting in the increase of mycotoxins in the food supply occur due to high temperature and moisture levels during pre- and post-harvest and during storage, transportation and processing, as well as pre-harvest practices and timing, the handling of agricultural products and insect damage.

Aquatic and fishery food sources can be affected by climate when more frequent or widespread harmful algal blooms lead to high toxin levels and uptake rates within the food supply, it said.

The report also noted that elevated atmospheric carbon dioxide leads to lower protein content in important global food staples.

It said diminished food utilization or utilization stability can result when the food system fails to adapt to changes in climate. Food safety and waste vulnerabilities are particularly apparent during extreme weather events when time is critical. Adaptive options can include increased and improved cold storage, varietal selection, biological control, storage structures, chemical treatments, botanical and inert dusts and improved handling and processing to reduce vulnerabilities.

On the topic of climate change’s impact on food utilization, the researchers noted that biological contaminants in the food supply are highly sensitive to changing temperature and humidity, affect food spoilage rates and human health, the latter of which in turn affects a body’s capacity to absorb nutrients. Although adaptive capacity is potentially very high, it also is highly variable, and depends on decisions made at multiple levels throughout a diverse food system.

Climate variability has already affected the stability of food utilization through extreme weather events, to the degree that more extreme events may be anticipated in the future, food utilization stability should be expected to be challenged, it said.