Hotter, drier, sicker? How a changing planet drives disease

BANGKOK, Thailand — Humans have made our planet warmer, more polluted and ever less hospitable to many species, and these changes are driving the spread of infectious disease.

Warmer, wetter climates can expand the range of vector species like mosquitos, while habitat loss can push disease-carrying animals into closer contact with humans.

New research reveals how complex the effects are, with our impact on the climate and planet turbocharging some diseases and changing transmission patterns for others.

Biodiversity loss appears to play an outsize role in increasing infectious disease, according to work published in the journal Nature this week.

It analysed nearly 3,000 datasets from existing studies to see how biodiversity loss, climate change, chemical pollution, habitat loss or change, and species introduction affect infectious disease in humans, animals and plants.

It found biodiversity loss was by far the biggest driver, followed by climate change and the introduction of novel species.

Parasites target species that are more abundant and offer more potential hosts, explained senior author Jason Rohr, a professor of biological sciences at the University of Notre Dame.

And species with large populations are more likely to "be investing in growth, reproduction and dispersal, at the expense of defences against parasites", he told AFP.

But rarer species with more resistance are vulnerable to biodiversity loss, leaving us with "more abundant, parasite-competent hosts".

The warmer weather produced by climate change offers new habitats for disease vectors, as well as longer reproductive seasons.

"If there are more generations of parasites or vectors, then there can be more disease," Rohr said.

Not all human adaptation of the planet increases infectious disease, however.

Habitat loss or change was associated with a drop in infectious disease, largely because of the sanitary improvements that come with urbanisation, like running water and sewage systems.

Climate change's effects on disease are also not uniform across the globe.

In tropical climates, warmer, wetter weather is driving an explosion in dengue fever.

But drier conditions in Africa may shrink the areas where