Impact of climate change on human health

The impact of biodiversity loss, climate change on human health


The world is experiencing a pandemic of unprecedented proportions and any assessment on biodiversity, climate change or environment is unlikely to hit the headlines. However, a recent report ‘Living Planet-2020’ by over 125 global experts from World Wildlife Fund (WWF) did receive some attention. The headline was a 68% fall in populations of monitored vertebrate species (mammals, birds, fish, amphibians and reptiles) between 1970 and 2016 an 84% wildlife populations found in freshwater habitat. In 2019, a report by Intergovernmental Platform on Biodiversity and Ecosystem Services (IPBES) concluded that nearly one million animal and plant species are on the verge of extinction, possibly within a few decades.

Natural ecosystems have declined by almost 47%. Seventy-five per cent of the earth’s ice-free land surface has already been significantly altered, oceans are polluted and over 85% area of wetlands has been lost. These global assessments have identified a few key drivers for the decline of our planet’s biodiversity-- overexploitation of natural resources, land-use change, climate change and pollution. The Food and Agriculture Organization (FAO) published a report on ‘The state of the world’s biodiversity for food and agriculture’ in 2019, which showed the declining trend in plant diversity on agricultural land and the growing number of animal breeds under threat. Nearly a third of fish stocks are overfished and a third of freshwater fish species are considered threatened. Thus, there is overwhelming evidence that biodiversity is declining at an unprecedented scale, threatening food production, including meat, dairy and fisheries. Many species that contribute to vital ecosystem services including pollinators, natural enemies of pests, soil organisms and wild food species’ populations are also on the decline.

When it comes to biodiversity, we generally associate more with iconic species such as tigers, elephants, pandas and polar bears. However, we do not recognize that millions of insects, bacteria and yet to be discovered species are also under threat. It is well known that biodiversity plays a critical role in providing food, fibre, water, energy, medicines and other genetic materials. It is also known that biodiversity is critical for regulation of climate, water quality, pollination services, flood control and storm surges.

We are also increasingly recognising that the loss of biodiversity and habitat destruction are linked to human health. Covid-19 is one in a long list of diseases that originate from wildlife. Other recent outbreaks include SARS, Ebola, avian influenza and swine influenza. As we continue to disturb ecosystems worldwide, we are likely to see more pathogens crossing from wildlife to humans. In fact, 60% of emerging infectious diseases could come from animals and nearly three-quarters of these from wild animals. These diseases can be transferred to humans in multiple ways--sometimes through direct contact with wild animals, and sometimes through intermediary hosts like domestic animals. One study estimates diseases that originate in animals cause 2.5 billion infections and nearly three million deaths annually. Given that many of the diseases originate from wildlife, preventing the next pandemic might depend on how we manage our relationship with nature. According to UNEP, more biodiverse an ecosystem is, the more difficult it is for one pathogen to spread rapidly or dominate; whereas, biodiversity loss provides opportunity for pathogens to pass between animals and humans. Pathogens tend to be 'diluted' in complex, undisturbed, ecosystems.

Apart from biodiversity, climate change and associated extreme events (droughts, floods, cyclones, hurricanes, etc.) are impacting species distribution, population sizes, the timing of reproduction and migration. There has also been an increased frequency of pest and disease outbreaks resulting from these changes which may have adverse impacts on agricultural production and human wellbeing. Climate change is increasingly exacerbating the impact of other drivers on nature and human wellbeing. The fourth National Climate Assessment, published in the US in 2018 highlighted how “higher temperatures, severe weather events and rising seas can contribute to heat-related cardiopulmonary illness, infectious diseases and mental health issues. Societal factors such as poverty, discrimination, access to health care and pre-existing health conditions make some populations even more vulnerable”. This is heightened in the Indian conditions, given the high levels of poverty and the pathetic state of public health infrastructure as demonstrated during the current Covid-19 pandemic. Global warming will increase the seasonal window and spatial spread of many vector-borne diseases such as malaria, chikungunya, dengue etc.

The decline in biodiversity and climate change will have a compounded effect on human health. The effects of drivers such as climate change, land and sea use change, overexploitation of resources, pollution and invasive alien species are all likely to exacerbate negative impacts on nature. Climate change is also leading to an increase in the frequency and intensity of droughts, floods, cyclones and may impact food production and nutrition.

The WWF report concluded that the destruction or alteration of the world’s natural systems threatens to undo the extraordinary gains in human health and well-being achieved over the past century. India will experience an increase in human population to about 1.5 billion in the coming decades, along with economic growth, and the need to lift hundreds of millions out of poverty; this will have serious implications for natural resources. We lack high-quality assessments like the global assessments mentioned above on the combined impact of climate change and biodiversity loss on human health, food production, freshwater availability. Given this absence, appropriate location-specific solutions cannot be developed. Finally, global level solutions and the necessary actions are available from the United Nations Paris Climate Change Agreement, Convention on Biodiversity and UN Sustainable Development Goals. Recently, the UN highlighted that our best vaccine for the future is to protect nature and biodiversity. Unfortunately, in the current pandemic and possibly in the post-pandemic era, climate change, biodiversity loss and environmental degradation will not be priorities and will likely result in severe negative consequences for health, food production and freshwater supply.

(The writer is a retired Professor of Indian Institute of Science)

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