Bangkok: Humans have made our planet warmer, more polluted, and less friendly to many species, and these changes have led to the spread of infectious diseases.
Warm, humid weather can expand the range of vector species such as mosquitoes, and habitat loss can bring disease-carrying animals into closer contact with humans.
New research reveals how complex the interactions between climate and the planet are, causing some diseases and changing transmission patterns for others.
The loss of biodiversity appears to be playing a major role in the rise of infectious diseases, according to work published this week in the journal Nature.
Nearly 3,000 databases of existing research were analyzed to see how biodiversity loss, climate change, chemical pollution, habitat loss or change, and disease affect species in humans, animals and plants.
It found that biodiversity loss is a major driver of climate change and the spread of new species.
Parasites are increasingly targeting species that offer more hosts, explains Jason Rohr, a professor of biological sciences at the University of Notre Dame.
Species with large populations “more likely to invest in growth, reproduction and dispersal at the expense of protection from parasites,” he said.
But rare species with great resistance are at risk of loss of biodiversity, leaving us with “more, host more parasite-competent”.
Warmer weather created by climate change offers new habitats for disease vectors, as well as longer breeding seasons.
“If there are more generations of parasites or vectors, there can be more disease,” Rohr said.
However, human adaptation of the planet did not increase the epidemic.
Habitat loss or change has been associated with a reduction in infectious diseases, mostly due to improvements in sanitation associated with urbanization, such as running water and sewage systems.
The impact of climate change on disease is not uniform across the globe.
In tropical climates, hotter, more humid air creates an explosion in sea fever.
But Africa’s drier conditions could reduce malaria hotspots in the coming decades.
The study published this week in the journal Science modeled the effects of climate change, hydrological processes such as precipitation and evaporation, and how quickly water sinks into the ground.
In areas prone to the spread of the disease, it is expected to decrease by 2025, compared to forecasts based on rainfall alone.
They also found that the fever season in parts of Africa may be four months shorter than expected.
The results are not necessarily good news, warned Mark Smith, associate professor of water research at the University of Leeds.
“The hot spot location will change,” he said.
People in those areas may be more vulnerable because they are not exposed.
The population is expected to increase rapidly in areas where malaria remains or is likely to be infected, so the prevalence of this disease may increase.
He warned that extreme heat conditions can also be bad for us.
Changes in the availability of water for drinking or agriculture can be very severe.”
The link between climate and infectious diseases means climate models can help predict viruses.
Local temperature and rainfall forecasts have been used to predict seasickness, but they offer short lead times and are reliable.
Indian Ocean Basin Wide Index (IOBW) may be the regional average of sea surface temperature anomalies in the Indian Ocean.
Also published this week in Science, this study looked at three decades of ocean data from 46 countries and found strong correlations with changes in IOBW and events in the northern and southern hemispheres.
The study was retrospective, so the predictive power of IOBW has not been tested.
But that monitoring could help officials better prepare for outbreaks, a major public health concern.
Ultimately, Rohr said, the rise of infectious diseases means fighting climate change.
The study “suggests that the increase in disease will be persistent and widespread in the face of climate change, and reduction of greenhouse gases will be necessary,” he said.
