A new article published in The Lancet Planetary Health cites “land-use induced spillover” as a major, and escalating, risk for new pandemic virus outbreaks. This is the leading theory as to how the SARS-CoV-2 virus, which causes the disease known as COVID-19, began to infect humans.
The authors frame the problem this way:
The rapid global spread and human health impacts of SARS-CoV-2, the virus that causes COVID-19, have led to calls for greater control of wildlife commerce and consumption. Although warranted in high-risk situations, these measures should be complementary to regulatory reforms to address land use change—the primary driver of pathogen transmission from wildlife to humans [1, 2]—a process known as zoonotic spillover.  When political and financial capital are wisely invested in measures to protect the health of ecosystems and their wildlife inhabitants, human health is a return on investment.
Land use change—which we regard as anthropogenically-induced ecosystem change—operates through various mechanisms from local to regional scales and can induce environmental stressors that determine the abundance and distribution of wildlife, shape the dynamics of wildlife exposure and susceptibility to pathogen infection, drive pathogen shedding or excretion from wildlife (panel), and create novel contact opportunities facilitating pathogen spread between species (spillover), ultimately leading to human infection and further spread. [1, 11] When land use change drives this infect–shed–spill–spread cascade, we refer to this process as land use-induced spillover (figure 1).
Land use change can be subtle or severe. When we talk about “deforestation”, for instance, we are often talking about the total removal of forest habitat and related ecosystems, not only in a particular piece of land, but in the surrounding landscape. Barren hillsides don’t behave, ecologically, like thick jungle.
Ecosystems are disrupted in a kind of ripple effect, which can cause many species in those ecosystems to change behavior radically and in suboptimal ways—because they are given no choice. Their behavior change or disappearance alters the biosecurity risk profile of an immediate area of disrupted habitat, but also across a wider regional ecological fabric.
We now know there is a pattern of risk that can be observed, and minimized. The risk of spillover depends on how widespread the virus is in the wildlife population, the extent of wildlife “shedding” of the virus, and the frequency of human contact with the pathogen shed from infected wildlife. This makes up “the infect-shed-spill-spread cascade”.
The more interaction people have with that cascade, the more likely a zoonotic or spillover virus will emerge in the human population.
The authors issue a call to action, for research, sharing of data, and new policy design processes, to achieve greater understanding of the spillover risk from patterns of land use change. The aim is to achieve new breakthroughs in biosecurity. They note that “Australia and New Zealand are developing broad biosecurity frameworks that integrate across environmental, agriculture, and human health sectors. ”
They add that:
Fostering landscape immunity should be regarded as a biosecurity imperative and actions need to be taken to maintain and enhance landscape immunity as part of the national and global security agenda.
The authors conclude:
COVID-19 has taught us that humanity is highly vulnerable to zoonotic disease pandemics. Fragmented landscapes and fragmented solutions increase this vulnerability.
In essence, we need to work consciously toward a healthier state of relationship with natural systems, so we don’t create additional nonlinear compounding risks due to habitat destruction, ecosystem loss or migration, and virus spillover. The COVID-19 pandemic emergency has made clear we cannot afford to continue adding biosecurity risk in our land use practices.
The article “Land use-induced spillover: a call to action to safeguard environmental, animal, and human health”, published in Volume 5, Issue 4, of The Lancet Planetary Health, was authored by Raina K Plowright, PhD †; Jamie K Reaser, PhD †; Harvey Locke, LLB ; Stephen J Woodley, PhD ; Prof Jonathan A Patz, MD ; Daniel J Becker, PhD ; Gabriel Oppler, BS ; Prof Peter J Hudson, PhD ; Gary M Tabor, VMD.