Italiano English
Download PDF

March of the parasites driven by global warming

Today, 10-16% of growing crops are lost to pests, with further losses occurring after harvest. In our globally connected world, there is great opportunity for pests to be spread across international borders. Indeed, it is estimated that more than half of plant diseases are spread by human introduction. However, once introduced, weather conditions are thought to be the main determinant of whether a pest or pathogen becomes established. The importance of weather has led to speculation on how the effects of climate change might affect pest distributions and, subsequently, food security. This study suggests that the warming climate is allowing pests to become established in regions that would have been previously unsuitable because they were cooler. The researchers analysed 612 published records of where crop pests and pathogens have occurred, including mites, aphids, fungi, bacteria, beetles, flies, butterflies and moths, amongst others. The latitude of occurrences was then plotted to investigate how ranges of these species have shifted since 1960. 
The results show that, although there was a large amount of variation between different groups, on average, there was a shift of 2.7 km per year towards the poles, with significant shifts for many important pest species. For example, fungi, bacteria, beetles, flies, butterflies and moths have all clearly been moving towards the poles in the past 50 years. One important factor that the researchers investigate is the possibility of a bias in the records of where pests and pathogens have occurred. They highlight the fact that scientific techniques and equipment are typically more advanced in countries at higher latitudes, i.e. closer to the poles. However, if such a bias existed it would lead to pests being first reported in countries closer to poles and only later discovered nearer the Equator. The trend observed in this study is that most pests are actually observed first nearer the equator and only later at higher latitudes, suggesting that it is the result of global warming, not data bias. 
In fact, the only groups that might appear as if they have moved towards the Equator, according to the observation records, are nematode worms and viruses. These are often both soil borne, and therefore more difficult to detect, especially in countries closer to the Equator with less technical capacity. In these cases, it may be bias in the data that explains the apparent ‘movement’, suggest the study’s authors. Although global food security depends on a variety of different interconnected factors, plant diseases and pests can have a drastic effect, especially in poorer countries. The findings in this study suggest that, in the face of climate change, increased investment in monitoring and preventing the spread of crop pests are needed.

In the picture: adult of Paysandisia archon moth, south america's lepidopter acclimated in the Mediterranean area of Europe 

Pests are moving to new habitats, to the North and the South Pole. Increase their range of distribution with the contribution of the global market

contenuto