A Gillette's checkerspot butterfly visiting sneezeweed. Credit: A. Miller-Rushing

As the climate has warmed, many plants are starting to grow leaves and bloom flowers earlier. A new study published in the journal, Nature, suggests that most field experiments may underestimate the degree to which the timing of leafing and flowering changes with global warming.

Understanding how plants are responding to climate change will help develop more accurate indicators of spring, forecast the onset of allergy season or the chances of western wildfires, manage wildlife and invasive plants, and help inform habitat restoration plans.

In this new study, scientists evaluated the sensitivity of plants to changes in temperature using two sources: experimental plots versus historical observations from natural sites.

The experiments analyzed in this study were conducted by artificially inducing warming in small study plots, and then measuring plant responses. The historical observations entailed long-term monitoring of multiple species at natural ecological research sites without any manipulation. The date of leafing and flowering was synthesized for dozens of warming experiments and monitoring sites across the Northern Hemisphere.

Scientists conclude that compared to warming experiments, historical monitoring shows temperature sensitivity to be four times greater for leafing and over eight times faster for flowering.

Recording how climatic variations and trends impact seasonal events in plants. Credit: A. Miller-Rushing

On average, the warming experiments predicted that every degree rise in Celsius would advance plants’ flowering and leafing from half a day to 1.6 days, while historical observations indicate a temperature sensitivity of about 5 to 6 days per degree Celsius. The finding was strikingly consistent across species and datasets. Conclusions from this study are based on analysis of more than 1600 plant species on four continents.

The study of how climatic variations and trends impact seasonal events in plants and animals is termed “phenology.” This includes when cherry trees or lilacs blossom, when robins build their nests, when salmon swim upstream to spawn, or when leaves turn colors in the fall.

The study was conducted by an interdisciplinary team led by Elizabeth Wolkovich, with the University of British Columbia, and Ben Cook, with NASA-Goddard. The study was funded by the National Science Foundation, the State of California and the University of California, Santa Barbara. The U.S. Geological Survey (USGS) and the USA-National Phenology Network (USA-NPN) also provided support and assisted with assembling and analyzing historical phenological observations and climate data.

Future Tracks: Experiments and Observations

Observing changes in the seasonality of plants in Concord, Massachussets. Credit: A. Miller-Rushing

The authors of the Nature paper recognize the value of both experiments and monitoring. They call for standardization of measurements and protocols as well as improvements in experimental design, and continuation and expansion of long-term monitoring efforts like the USA-NPN.

The USA-NPN brings together citizen scientists, government agencies, non-profit groups, educators and students of all ages to monitor the impacts of climate change on plants and animals in the United States. The USA-NPN was established by the USGS in collaboration with the National Science Foundation.

“This study underscores the reasons for recent establishment of a USA-NPN to help track, understand, and hopefully forecast different species responses to climate variability and change across the U.S.,” said USGS scientist Julio Betancourt, who is a co-author of this new report.

You Can Help! Track the Pulse of our Planet

We need your help to track the pulse of our planet. Through the USA-NPN’s Nature’s Notebook, citizens across the nation are providing data on plants and animals.

People like you — gardeners, farmers, birders, hikers, anglers, joggers, or all-around nature enthusiasts — are already recording the recurring events they see in the lives of the plants and animals around them. This includes when cherry trees or lilacs blossom, when robins build their nests, when salmon swim upstream to spawn, or when leaves turn colors in the fall.

Become involved and sign up through the USA-NPN website, or contact the USA-NPN Executive Director Jake Weltzin at jweltzin@usgs.gov.

Mining bee on great false leopardbane in Concord, Massachusetts. Credit: A. Miller-Rushing

More Information

Read a University of California, San Diego, press release, as well as a NASA feature, on this new article.

Young boys working in a newly cropped field in Africa.

In parts of eastern Africa, drought is of increasing concern, as poor families suffer from food shortages and the inability to grow crops and sustain livestock. Stunted growth in children due to malnutrition has also been linked to climate trends in Africa.

Drought conditions are expected to continue as global temperatures continue to rise and rainfall declines across parts of eastern Africa.

This poses increased risk to millions of people in Africa who currently face potential food shortages.

What’s being done to help?

The USGS is involved in a variety of research efforts to help understand current and future conditions in Africa, helping to inform plans to provide aid.

The Famine Early Warning Systems Network, or FEWS NET, is one endeavor that has already made great strides in helping to address this issue. FEWS NET helps target more than $1.5 billion of assistance to more than 40 countries each year.

FEWS NET examines the populations of the developing world with the most food insecurity, identifying critical situations in which food aid will be needed. These are populations whose livelihoods are typically tied to subsistence rain-fed agriculture and pastoralism.

FEWS NET is sponsored by the U.S. Agency for International Development (USAID) Office of Food for Peace and the USGS is actively involved.

FEWS NET at the United Nations Climate Convention

A USGS presentation on FEWS NET will be a featured side event on November 30, 2011, at the United Nations 17^th annual Conference of the Parties (COP-17) in Durban, South Africa. The convention’s purpose is to develop international agreements and a declaration of policies and practices for combating climate change and its impacts around the world.

A herder moves cattle through a barren landscape in eastern Africa.

Climate forecasts and remote sensing help spot future trouble

FEWS NET has developed its own climate services to provide decision makers with early identification of agricultural drought that might trigger food insecurity. Scientists use climate forecasts to develop forward-looking food security assessments that are based on expected agricultural outcomes for the season ahead.

Since networks of ground observation stations are often sparse or reported late in FEWS NET countries, satellite remote sensing of vegetation and rainfall fills in the gaps. Remote sensing from space allows for rapid, accurate assessments of a broad range of environmental and agricultural conditions. USGS scientists provide the technologies and expertise to support remote sensing for FEWS NET activities.

Early warning of famine in Somalia helps pre-position food supplies

On July 20, 2011, the United Nations declared parts of Somalia as a region of famine. The decision was supported by FEWS NET and USGS observational evidence of conditions in the area.

The declaration was the culmination of early warning communications encouraging — months before the crisis — that government and other agencies pre-position food and supplies in the region.

“None of the many uses of Earth-observing satellites is more vital — or has as much potential for prompting timely humanitarian intervention — as famine early warning,” said USGS Director Marcia McNutt. “Remote sensing from space allows USGS scientists to provide rapid, accurate assessments of a broad range of environmental and agricultural conditions.”

The eastern Horn of Africa, the continental region that encompasses Somalia, has experienced two consecutive seasons of very poor rainfall resulting in the worst drought in 60 years. Crops have failed, livestock deaths are widespread, and food prices are very high. While the rains this winter have been good, food prices remain high, and the food security situation remains insecure.

Stunted growth linked to malnutrition and climate change

Other USGS research is helping to identify the impacts of a changing climate on Africa’s people. Scientists recently discovered that malnutrition and dry hot living conditions are linked to stunted growth in Mali, West Africa.

USGS research found that Mali was becoming substantially warmer and a little bit drier. Scientists also knew that farmers and those who make a living raising sheep, cattle, goats, or camels were poor, and that stunted growth was occurring throughout Mali.

Scientists wondered if there could be a link between human health and increasingly warm and dry conditions.

To investigate, the USGS worked with the University of California, Santa Barbara, to study climate observations and demographic and health data. The Demographic and Health Survey program routinely compiles data from surveys in 90 countries to study trends in health and population. Scientists analyzed statistics on specific villages in Mali and found that there was a link between a warmer climate and increased stunting.

Population growth combined with the impacts of warming will further increase these health impacts.

Stunting was also linked to other factors, such as mother’s education and the water supply system. Women’s education, improved water supplies, and agricultural development could help to address malnutrition and stunting in Mali.

An article on this research was published in in the journal, Applied Geography, by San Diego State University, the University of California, Santa Barbara, and the USGS.

A Food Security Assessment in Somalia found severe impacts on livestock due to drought conditions.

Other studies underway

Other new research includes the discovery that the warming of the Indian and western Pacific oceans (which is linked to global warming) affects rainfall over large areas of the Horn of Africa. As the globe has warmed over the last century, the Indian Ocean and western Pacific have warmed especially fast.

The resulting warmer air and increased humidity over the Indian and western Pacific oceans produce more frequent rainfall in that region. The air loses its moisture during rainfall, and then flows westward and descends over Africa, leading to decreased rain in parts of eastern Africa. Trends toward increased frequency of drought that we are seeing now are likely to continue into the future as warming continues.

A few recent articles on this research were published in the journal, Climate Dynamics, by scientists with the USGS, the University of California, Santa Barbara, and Los Alamos National Laboratory. The most recent article concludes that global warming will lead to a decrease in rainfall during the summer monsoon season, from June to September, across southern Sudan, southern Ethiopia, and northern Uganda.  Another article concluded that eastern Africa, particularly Kenya and southern Ethiopia, will also have a significant decrease in rainfall during the long-rains season from March to June.

USGS scientists are working hard to translate these technical studies into reports for decision makers. To date, they have completed summary fact sheets focused on Sudan and Kenya.

Scientists also found that some regions, like northern Ethiopia, are not getting drier due to current warming temperatures. Rainfall varies dramatically across all of eastern Africa, with high mountainous areas typically receiving many times the rainfall received in low-lying areas. Therefore, agricultural growth in these climatically safe regions could help offset rainfall declines in other locations.

Start with science

Scientists are looking at clues and changes in nature to understand the impacts of global warming. In Africa, impacts are seen across the landscape — on farms and even in humans.

By starting with science, well-informed decisions can be made to help Africa as it faces drought, famine, and health concerns.

FEWS NET partners include the USAID, Chemonics International, the USGS, NASA, NOAA, and the USDA. The Geography Department at the University of California, Santa Barbara, is a partner to the USGS in this effort.

Want more information?

Listen to a podcast interview with USGS scientists as they discuss ongoing efforts to understand conditions in Africa.