In the past two and a half centuries, the explosive growth in human population has led to increasing demands on our natural environment for resources such as food, fresh water, land, and energy. These benefits are provided to us by the interactions between living and non-living components of ecosystems, termed “ecosystem services”.

The concept of ecosystem services is intimately linked to ecosystem health – healthier, more diverse ecosystems provide greater benefits to us. Numerous international organizations, such as the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES), Intergovernmental Panel on Climate Change (IPCC), and World Wildlife Fund (WWF), have conducted studies to understand how human activity affects global ecosystem health. The IPBES’s 2019 Global Assessment Report identified human-driven climate change as one of the major contributors to the global deterioration of ecosystems.

What most studies agree on is that we are overtaxing our ecosystems at an unsustainable rate, drastically reducing ecosystem biodiversity and function. “Biodiversity and nature’s contributions sound academic and far removed from our daily lives,” said Sir Robert Watson, Chair of the IPBES. “Nothing could be further from the truth – they are the bedrock of our food, clean water and energy.”

To respond to the current ecosystem crisis requires an understanding of how our ecosystems are changing and what impact this has had on our health and livelihoods.

Poleward migration

Average global temperatures have increased by about 1.0°C since pre-industrial times. This has caused a poleward shift in geographical distributions for many species, particularly highly mobile insects, towards cooler areas that were previously unfavourable.

This phenomenon has had direct impact on food security and human health, as insects are common carriers of both plant and human diseases. A 2013 study found that crop pests across the world have migrated poleward at a rate of almost 3 km per year since 1960, exposing crops to new diseases. At a regional scale, there has been an increased prevalence of tick-borne diseases such as Lyme disease in Canada due to greater tick abundance, activity, and range as a direct result of warmer temperatures.

Altered precipitation

Increasing temperatures have led to greater surface water evaporation and water retention by air, causing changes in global precipitation patterns. Accelerated melting of glacial ice caps has also introduced cold fresh water to the ocean, which new studies suggest are altering ocean currents that play an important role in climate regulation. The net effect is that wet areas become wetter and dry areas become drier, leading simultaneously to more flood and drought events across the world. We have seen this play out in the past 6 months alone, with the extreme Australian bushfire season and severe flooding in East Africa.

Altered precipitation patterns are also affecting water security and patterns of disease outbreaks. In their 2018 Regional Assessment, the IPBES reported that the amount of available fresh water in the Americas has decreased by 50% since the 1960s. An increasing spread of cholera outbreaks in Asia and Africa have also been linked to warmer temperatures and increased precipitation, which favour transmission of the water-borne cholera bacterium.

What lies ahead

Although the effects of human activity on global ecosystems are extensive and, in many cases, irreversible, there is still time to act. As the Intergovernmental Panel on Climate Change writes in their 2019 Special Report on Global Warming of 1.5°C, “Every bit of warming matters, every year matters, every choice matters.”

A recurring theme of these global assessments is that the knowledge of how to protect our environment is already in our hands. What we require now are policies informed by the scientific findings to provide long-term solutions to slow down and mitigate the effects of climate change.


1: 2006 Millennium Ecosystems Assessment

3: IPBES 2019 Global Assessment

4: IPCC 1.5C Report

5: range shifts

6: crop pests range shift

7: tick-borne disease

8: precipitation and climate change

9: ice melt and ocean currents

10: cholera and climate change

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Karen Yeung

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