Plants help wildlife thrive, yet some threats continue to endanger their health

This year’s World Wildlife Day, we celebrate the awe-inspiring functionality and beauty of the green that surrounds us. Plants and vegetation are far from being a simple backdrop to the rest of humanity: they sustain life on Earth. But just like animals and humans, they are being affected by world-changing events, including the climate crisis and other man-made activities. This makes it urgent for One Health practitioners to envision and enable a future where ecosystem interdependence is enhanced by shifted mindsets, ecological strategies and renewed efforts to ensure everyone’s health.


From feeding terrestrial animals to providing a critical infrastructure to underwater natural beings, plants play a key role in the global health ecosystem, from land to sea. They clean air and water, build soil and support other living things.  It’s not a one-way street though – right next door, a whole world of thriving animals quietly enables plants to flourish. 

Although largely unseen, animals – including wildlife – are crucial for the wellbeing of plants. From pollination to seed dispersal and nutrient cycling, they play a vital role in sustaining the plant ecosystem as we know it, providing services that are essential for its survival. The mutually beneficial relationship between the animal and plant worlds has created a web of self-reinforcing living networks unlike any other. When one thrives, so does the other.

Some species, such as great apes, have even discovered how to use plants for their own healing. Humans have long observed wild animals throughout this process and then adapted these behaviors into human medicine. This highlights how a healthy animal-plant-human chain can make the world a better, healthier place. But as Earth’s environments become increasingly interconnected, there are threats to plant ecosystems that have become impossible to ignore.

Protecting plants under water 

Plants are everywhere around us, even in places we don’t get to see or experience every day. Just think about the vibrant ecosystem of plants living underwater. Aquatic plants play a crucial role in maintaining the health of aquatic ecosystems, including aquatic animals and wildlife. Their tasks include supplying reliable food source, producing oxygen, improving water quality and providing habitat for a wide range of fish and wildlife. They even offer safe areas for a variety of species, offering shelter for fish and invertebrates.

This close-tight relationship highlights how the health of aquatic plant communities is crucial for supporting resilient aquatic animal populations. It’s essential for these invaluable plant resources to survive in the wild. But this symbiotic experience also means that aquatic species may easily be affected by the recurrent issue of toxicity affecting plants. Whenever there is a lot of rain, the biological composition of plants, in fact, can change. Some species then get easily affected by a neurotoxin produced by algae. Among the more susceptible species are fish, aquatic invertebrates such as snails and zoo plankton. Interestingly, some underwater plants can be affected by agricultural runoff.

Many of these valuable underwater plants face further threats from habitat destruction, overharvesting, climate change and unregulated or illegal trade. Raising awareness, strengthening regulations and ensuring the sustainability of harvesting and trade have become important action points. “Conservation of aquatic plants is a global priority. This is also a powerful reminder that we need to stick to a One Health approach, as we know plant health is one of the pillars of ecosystems’ integrity”, says Dr Mwansa Songe, Member of the WOAH Working Group on Wildlife. “Everything needs to be addressed as a single system. It has become crucial for players in the policy field to take the lead with a holistic approach. This is the only way to prevent and mitigate threats at their source.”

A toxic legacy: how lead poisoning threatens global health  

Changes in the weather are not the only factor that has been endangering plant health. Another phenomenon is putting plants under threat, with severe health and ecological impacts: lead poisoning. Primarily caused by ingestion of lead from ammunition and fishing tackle, lead pollution can have catastrophic consequences for the plant-wildlife chain.

The high density of lead has made it the ammunition of choice for centuries despite its toxicity. The impacts of lead shot ingestion and poisoning in wildlife have been observed since the nineteenth century. When plants grown in contaminated soil, such as near shooting ranges or wherever hunters discharge high volumes of shot, they absorb high concentrations of lead in their tissues. This heavy metal exposure causes reduced growth, with studies on important agricultural forage species like Festuca arundinacea, Trifolium pratense, and Medicago sativa showing up to 30% lower shoot heights and shorter roots. Photosynthetic pigments also decline, impairing vitality, while lead transfers up the food chain – from plants to herbivores and then predators – risking widespread ecological toxicity. Lead ammunition deposited on agricultural land creates two pathways of exposure for animals and humans. Firstly, the heavy metal can be absorbed by plants used for human consumption as well as by grazing ruminants delivering milk and meat, and secondly, livestock can directly ingest lead shot or bullet fragments, so contaminating milk, meat and eggs and poisoning the animals.

Every year, millions of birds are poisoned to death following ingestion of lead shot mistaking them for food items or grit used in their gizzards to grind up food. Scavengers like eagles and vultures, often our most threatened species, are dying across the world from lead shot or bullet fragments left in hunted game. These birds inadvertently swallow the fragments in prey and carrion, then their strong stomach acid dissolves the lead pieces, letting it flood into their blood. Scavenging mammals are exposed to these bullet fragments too and can be poisoned, but mortality is higher in birds due to the level of exposure and their unique digestion system.

Lead poisoning also causes a range of sub-lethal impacts – birds’ ability to fly is affected, causing collisions with infrastructure such as power cables and a compromised immune system for wild species.

We have to think about health holistically, an individual with a compromised immune system is at far greater risk of infectious disease. In times of an unprecedented highly pathogenic avian influenza pandemic we do not need less and less resilient wildlife populations, not only for their own sakes but for risks to other sectors too.

Dr Ruth Cromie, WWT Research Fellow.

Beyond the toxic legacy created by contamination of soils by the 10,000s of tonnes of lead ammunition released every year, and the wildlife and livestock affected, people are at risk too.

This really is a One Health problem. Recognising that lead affects nearly every system in the human body, firing such a highly toxic substance into your food is an extraordinary thing to do.

Dr Ruth Cromie, WWT Research Fellow.

“The potent damaging effect of lead on the developing brain is very well understood. Maybe hunters do not mind risking increased risks of blood pressure and kidney disease but when they are feeding lead-killed game meat to their children they are putting them at serious risk of neurological harm.” adds Cromie. For others buying game meat, the lack of regulatory maximum lead levels leaves consumers exposed and in a regulatory fog.

Despite the known risks, solving the problems has proved hard because of a combination of cultural factors and industry resistance. Non-toxic alternatives do exist, but without regulation to embed their use, change is pitifully slow. Cromie knows that in the future we will look back and wonder why we did not prevent the use of lead ammunition sooner but is still hopeful that policy makers will follow the evidence, recognise the One Health benefits to be gained from using non-toxic substitutes and put health protection first. Along with regulation, there are needs for further research and development and improved access to alternatives that respect our shared ecosystems – especially in underserved areas – and resources to help hunters switch to non-lead tools. This will also translate into a substantial reduction in wildlife mortality and associated welfare benefits that will only have positive effects on everyone’s health.

From pharmaceuticals seeping into waterways to veterinary drugs disrupting ecosystems and heavy metals poisoning animals across the globe, The World Organisation for Animal Health (WOAH) recognises the challenges that wildlife and our interconnected ecosystem faces. Yet, solutions are possible through One Health. Managing these major global health risks cannot be done in isolation or by one sector alone. The approach goes beyond single diseases and calls for the full cooperation of the animal, human, plant and environment health sectors. In the light of this, WOAH continues to bring its expertise in animal health and welfare to diverse, much-needed multi-sectoral partnerships.