A Pesticide Odyssey
Federico Maggi
School of Civil Engineering, The University of Sydney, Sydney, NSW, Australia
Fiona H.M. Tang
Department of Civil Engineering, Monash University, Clayton, VIC, Australia
Francesco N. Tubiello
Statistics Division, Food and Agriculture Organization of the United Nations, Rome, Italy
Winning article: Agricultural pesticide land budget and river discharge to oceans (Nature, 2023)
“This study is foundational in the quest to quantify pesticide levels in the environment to safeguard the integrity of our ecosystems within planetary boundaries”
Our planet faces an unprecedented challenge when addressing contamination caused by myriads of materials resulting from human activities. Either discovered or refined, result of invention, or derived from our activities, the Earth is bearing the collective burden of substances that are accumulating in the environment at an ecologically intolerable pace. One category of pollutants that has gained particular attention is chemical pesticides, introduced in agriculture with the intention to reduce risk of loss in production. The task was achieved successfully, albeit at the great cost of inadvertently exposing the ecosystem and non-target organisms to unwanted toxicity. Despite the initial hope of achieving an equilibrium between agricultural productivity while maintaining healthy environmental functions, decades of extensive research have shed light on the scale of adverse effects of pesticides across various domains. Particularly, loss of biodiversity, degradation of water, soil and air quality, and adverse effects on the fitness of non-target organisms, including on human health, are widely reported in the scientific literature. In contrast to this, only sparse, poorly funded initiatives, seek ways to reduce the dependence of agriculture on chemical inputs. It is now imperative for us to derive firm numbers on how much pesticide is used and the routes through which it moves in the environment, especially in terms of mobility pathways and residues to use in decision making to address this imbalance and take decisive steps towards minimizing, if not completely eliminating, the threats caused by these contaminations.
Figure 1. First published in Maggi, F., Tang, F. H., & Tubiello, F. N. (2023). Agricultural pesticide land budget and river discharge to oceans. Nature, 620(7976), 1013-1017.
The journey of our research team in the understanding of pesticide contaminations began with the possibly most simple question – where do the dangerous chemical agents in pesticides go after they are released in the field? Yet, to answer this fundamental question we needed to fill a huge void of knowledge regarding how individual pesticides interact with the environment spanning from defining and quantifying the dangerous agents being used, their application rates by crop and location around the globe, and the environmental processes controlling their breakdown or leading to accumulation in sensitive environments such as surface waters and biodiversity-rich hotspots. We designed and tested a rigorous predictive tool, a planetary “digital twin”, that is a full-scale computer model of Earth enabling us to track pesticide movement in the environment in time across lands and within hydrological units and streams, and their transport all the way downstream to oceans. Our research is the first of its kind to provide a detailed picture of pesticide flows in the environment. We monitored minutely the journey of individual pesticides from their application points and what we found was shocking. These hazardous active substances move across extraordinary wide geographic scales to the end points, reaching practically all aquifers and oceans. Of the 3 million tonnes pesticides used annually in agriculture, 10% remains in the upper soil horizons as residue while 7% leaches into the aquifers, and 0.1% enters rivers and oceans (Figure 1). More importantly, our planetary digital twin allows us to predict to high accuracy the outcomes resulting from changes in practice of pesticide use so we are able to show farmers directly and compellingly how even small changes in use can have hugely beneficial results for the local and global environment. This is an unprecedented capability that can be used in aiding the design of tailored strategies to decrease contamination locally and measure their efficacy over time.
The philosophy embodied in our recent works on contaminations, and specifically in the winning work, is that investing in truly unexplored research is paramount to produce the new knowledge needed to develop real life, innovative solutions to global planetary challenges. The digital planetary twin we developed, when used in conjunction with field measurements, offers a powerful and cost-effective means for tracking pesticide concentrations in the environment. Thanks to its high-level mechanistic process accounting, our model can be used to understand factors controlling pesticide transport and accumulation in the environment as a function of real-world hydrological flows and agricultural practices alike. For example, it can be used to predict how changing climate patterns may impact the environmental fate of these substances. Within the Planetary Boundary framework first of all, but also in other international initiatives such as the Sustainable Development Goals, our work and modelling tool help to inform risk prevention planning, hotspot identification, and recommendations for safe application levels to reduce risk to biodiversity and human health. Particularly in the private sector, the capabilities to identify and predict pesticide environmental persistence can provide critical guidance towards less-damaging alternatives, enhancing environmentally responsible practices and aligning with the growing global demand for sustainable solutions, thus facilitating pesticide manufacturers to develop eco-friendly technologies and agrifood producers to adopt conservative practices.
In summary, in an ideal Earth where society as a whole agrees on zero tolerance for chemicals (pesticides) contamination, our work reports pathways and quantities of pesticide residue in the different environmental compartments including in soil and surface river waters, and the fluxes of pesticide to the deep aquifer as well as via rivers to oceans. These metrics enable us to measure how much we are off the ideal target. On the one hand, an emphasis on a zero-tolerance approach reflects a strong commitment to uncover the extent of the issue, offering at the same time a means to actively target mitigation of these impacts. On the other hand, a zero tolerance on contamination is a stimulus to uncover whether there is a way for the global food supply chain to minimize their use without causing contaminations. By providing a comprehensive understanding of pesticide movements, our research supports the development of strategies to reduce contamination at both local and global levels, with the ultimate auspice to achieve “no contamination”.
This field of research, and the winning work in particular, is charting the current state-of-the-art with respect to contamination studies that involve global geospatial mapping, big data and powerful computational methods. Yet, we are confident that a wider scientific community is key to continue to grow this interdisciplinary field in its reach and importance similarly to what climate change modelling and forecasting experienced in the past two decades. For the potential of our work to be realised, education is the essential tool in the quest for impactful and lasting environmental stewardship. By infusing a sense of responsibility and awareness in current and future generations, we can foster a culture of environmental respect and preservation. Understanding the consequences of contamination, especially at a “big picture” planetary level, will imbue a nurturing awareness of the importance of sustainable practices, ensuring that individuals are equipped to make informed choices that contribute to a healthier planet. This participatory understanding, along with novel approaches in environmental law and justice, might finally bring our Earth at the centre of our environmental and ethical stewardship, so that we truly begin to respect and care for our world as it – and we – deserve.
Photo 1. Federico Maggi, Fiona H.M. Tang, and Francesco N. Tubiello.
