Is Climate Change Encouraging the Spread of Dangerous Diseases?

Unprecedented plagues and diseases are threatening crops across the globe, and the results could be disastrous according to scientists.

Bananas are one such crop that has fallen victim to a variety of bugs and fungal infections, which are spreading so rapidly that the government in Costa Rica, one of the biggest suppliers of the fruit, has already declared a “national emergency”, amidst serious concerns that the country would not be able to meet its export obligations.

Plagues of mealybugs and scale insects have decimated over 20% of the crop yield; the insects weaken plants and cause blemishes on fruit, rendering them useless for the retailer and consequently causing huge batches to be written off.

Magda Gonzalez, the director of the agriculture ministry’s State Phytosanitary Services (SFE), is convinced that climate change is to blame, as changing environments have enabled the pests to proliferate.

“I can tell you with near certainty that climate change is behind these pests,” she said, adding that it was likely that similar plagues would be seen worldwide.

Banana crops are also being afflicted by a new strain of banana-eating fungus called Fusarium oxysporum f. sp.cubense (Foc), which is threatening to seriously affect all major global producers, according to a recent report in Scientific American.

“It’s a gigantic problem,” said Rony Swennen, a breeder at the International Institute of Tropical Agriculture in Dar es Salaam, Tanzania.

Researchers have discovered that the fungus, which was thought to be restricted to Asia and Australia, has now been reported in Jordan and also in Mozambique, and it seems that most cultivars of banana are vulnerable to the new variant of the fungus.Scientists are extremely worried that the Foc-TR4 strain could pose a risk to banana exports across the whole of Latin American and the Caribbean, areas that provide over 80 per cent of the world’s supply.

Gert Kema, a Fusarium researcher at Wageningen University and Research Centre in the Netherlands, co-authored a report on the disease in Jordan.

He told Scientific American: “I’m incredibly concerned. I will not be surprised if it pops up in Latin America in the near future.”

Research studies are already being conducted in Latin America to predict the spread of pathogen vectors into that area, and the predictions are sobering. A recent study in Chile suggested that it could soon become host to one of the most potent pests, the Pink Hibiscus Mealybug, a predator that already assaults a wide range of crops in Florida, including citrus, avocado, carambola, fig, guava, mango, soursop, and sugarcane, and is a growing threat in many other countries.

The Chilean study, which was published in the journal Climatic Change, warned that "climate change projections indicate that a larger region would fit as potential habitat for this pest, allowing it to persist over time and colonize a larger proportion of the Chilean territory."

Bananas are not the only crop to be currently affected by severe pest infestation: Florida orange crops are being assailed by a tiny terror known as the Asian citrus psyllid, which has annihilated recent crops and threatens to seriously squeeze consumer’s purses by sending juice costs rocketing.

The pint-sized predator infects citrus trees with a malady called "citrus greening disease", colloquially known as "huanglongbing" , a term derived from the Chinese which literally translates as "Yellow Dragon Disease".

The vector-borne disease causes fruit to taste bitter and drop from trees too early, and seems to be resistant all insecticide, fertilizer and extra mineral treatments.

"It feels we are losing the fight," said Ellis Hunt, the head of a family-run citrus farm in the Florida town of Lake Wales, where the disease has cut annual production from one million boxes of fruit to 750,000.

The U.S government has lowered its forecast for the forthcoming harvest four times, with the latest figures released by the U.S. Department of Agriculture predicting an output of 110 million boxes of fruit, around 4.95 million tons, an 18 per cent reduction on last year’s yield, and the lowest since 1985. A huge investment has been made to fund research projects focused on exploring methods to counteract the disease; citrus-growing is a $9 billion industry in Florida alone and provides employment for 76,000 people, so the authorities are desperate to find a solution.

Diseases affecting our crops may not be the only result of climatic changes: melting permafrost has already unleashed an ancient virus that has lain dormant for over 30,000 years.

A French team led by Jean-Michel Claverie and Chantal Abergel of Aix-Marseille University in Marseille, France, discovered the unknown virus which has been christened Pithovirus sibericum. The researchers were able to revive the inert virus under laboratory conditions, and found that the virus was still active and quickly infected the host cel, an amoeba.

"We use amoeba on purpose as a safe bait for capturing viruses. We then immediately verify that they are not able to infect animal/human cells," stressed the researchers.

The findings have been published in the Proceedings of the National Academy of Sciences, and have raised concerns that climate change and also deep mining could result in dangerous bugs being released back into circulation:

"Mining and drilling means … digging through these ancient layers for the first time in millions of years. If ‘viable’ [viral particles] are still there, this is a good recipe for disaster," said Claverie and Abergel.

Other experts were keen to dispel any alarm, and said the risk from potential pre-historic pathogens was very small:

"The idea would make a great movie but is extremely unlikely unless the virus came from a frozen human being who possibly died from a virus that is no longer in circulation," said Edward Mocarski, a professor of microbiology at Emory University. "A very small proportion [of the viruses on Earth] represent viruses that can infect mammals and an even smaller proportion pose any risk to humans."

Whether global warming will release long-dead viruses that threaten humanity only time will tell, but it seems certain that it is implicated the unprecedented increase in the pathogens that are already threatening our food supplies. This latest rash of pests affecting our crops could become commonplace as natural environments are altered by the onset of global warming and become more conducive for pest proliferation. This is one of the less obvious affects of climate change, but one which could ultimately become one of those with the most impact on our daily lives.

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