Our need to feed an ever-increasing population is creating an ecological dilemma, writes Dr George Crisp
In our physically insulated urban environment, and with our cognitively divorced economic world, it is all to easy to overlook the importance of nature.
“Nature” or, more specifically, the ecological services it provides, is absolutely essential to us in supporting our health and wellbeing, and our economy.
Perhaps the most obvious is through the provision of food, shelter and fibre, and also of medicines. And while we tend to think that modern medicines are synthetic pharmaceutical products, this far from true.
Most new drugs are discovered by testing the innumerable substances that are found in flora and fauna. Antimicrobial, analgesics, chemotherapy agents, anti-hypertensives and statins are examples of important naturally derived therapeutic classes. Some of these substances still cannot be manufactured de novo.
As well as provisioning, ecosystems give us regulatory services; removing toxic waste products and pollutants from soil, water and air and recycling nutrients. They also play an important role in modulating local and regional climates. Even in our modern cities, trees and green spaces reduce urban heat and air pollution and mitigate the risk of flooding.
Natural systems regulate many infectious diseases. There is a consistent pattern – loss of biodiversity tends to promote both infectious transmission of disease and its incidence.
Some animals are better disease vectors and hosts. Greater diversity results in more incompetent hosts for vectors to bite, leading to a “dilution” effect which limits disease transmission.
A reduction in host diversity appears to be a factor in Lyme disease, where people living near fragmented forests have a greater risk of being infected.
Mosquito diversity declines when areas become deforested. It is also observed that the species that then dominate tend to be those that more efficiently transmit malaria.
Natural systems also provide barriers that insulate us (and other species) from potential pathogens. When those barriers break down, novel infections can occur, such as HIV and SARS.
Production of many of our agricultural crops relies on ecological supporting services. In addition to insect pollination, an apple tree involves at least nine different species to produce its fruit.
Nature also provides important aesthetic and cultural services.
Loss of biodiversity tends to promote both infectious transmission of disease and its incidence.
There are even direct health benefits. Studies consistently show that just being “exposed” to natural surroundings can improve both physical and mental health outcomes.
Ecosystems clearly provide a wide range of services that we depend on, and the integrity and resilience of those ecosystems in turn depends on the genetic and species biodiversity that constitute them.
There are almost two million different known species on earth and an estimated 15 million in total, but the rate of species extinction has escalated over recent decades to levels of between 100 to 1000 times the background rate.
This realisation led Lord Martin Rees, former president of the Royal Society, to proclaim: “We are erasing the book of life before we have even read it.”
Historically, this acceleration in biodiversity loss has resulted from land clearing for agriculture and over-harvesting of wild species.
It’s estimated that we now use around 27% of the planet’s land (an area the size of Africa) for livestock and 13% (the size of South America) for crop production.
To feed the world’s swelling population, the combined area is projected to rise to 70% within a few decades.
We need to produce more food, and despite that productivity being dependent on biodiverse ecosystems, our modern agricultural method is a powerful driver of further biodiversity loss.
Dr George Crisp is a General Practitioner and WA chair of Doctors for the Environment, Australia
