IF WE WERE to close our eyes and imagine a world without animals, what would it look like? It’s not that difficult to imagine a planet devoid of humans or other animals.

Now try and imagine a world without plants. It’s almost impossible to conceive. Although we sometimes take them for granted, plants have made possible and shaped life on Earth while making this a truly green planet.

Plants are at the centre of many of the most crucial global issues that face us now and will face us in the century to come. How can we ensure that a growing human population has enough food to eat? How can we produce that food and, at the same time, reduce the environmental impact of crop production and agriculture generally? How can we reduce the impending threat of global warming?

Can we use plants to power our homes and cars? How do we maintain global biodiversity and use medicines produced by plants to cure diseases and promote human health? All these questions and more require us to look again at our relationship with plants and how they can ultimately be useful to our society and economy.

Plants have shaped the world we live in

Looking back through time, plants have shaped the world we now live in and are ultimately responsible for creating the conditions for human life to exist on Earth in the first place. When the earliest land plants appeared on Earth about 450 million years ago, they drastically changed the Earth’s atmosphere; reducing the amount of carbon dioxide and increasing the level of oxygen. That change allowed other organisms to evolve and flourish – some of them, our evolutionary ancestors.

Green plants are nature’s solar panels that have colonised much of the planet. Through a powerful process called photosynthesis, plants are capable of harnessing the vast energy radiating from the Sun. They can then make that energy available to animals, which lack this amazing ability to gather energy from an extra-terrestrial source. The Sun is the ultimate source of all energy in our solar system but we would have no way to access that energy without plants.

Our use of plants to produce food is, perhaps, the most central element of the human connection to this green planet. Since the earliest of farmers, 10,000 years ago, humans have sought to (subconsciously at first and then, more and more, consciously) select for plant types and varieties which gave the most fruits, tastiest tubers or most stable yields. Now, we’ve got more powerful tools at our disposal for plant breeding, but the basic process is essentially the same – select the best plant from this year’s crop and grow its seed next year.

The importance of plants to health and economies

But growing plants for food is just one of the ways in which we utilise them in the modern world. The ancient Egyptians once chewed willow bark to reduce fever and headaches. Now we know that the bark of willow contains the active ingredients of aspirin. More recently, a chemical derived from daffodils has been used to treat Alzheimer’s disease and cancers have been treated with the medicine taxol, derived from the yew tree. Plants are also gaining attention as “edible vaccines”, where vaccines for diseases like HIV could be produced in a plant that might also act as a delivery vehicle.

The Irish government seem to recognise the importance of plants to Ireland’s economy. If we look at the 2012 Action Plan for Jobs, sectors highlighted for potential job creation include the “Green Economy” and “Agri-food production”.  Both of these sectors have plants at their centre. Tourism – another sector flagged for growth – also relies heavily on Ireland’s natural landscape and our native flora.

Taken together with the fisheries sector, the agri-food industry in Ireland directly employs about 150,000 people and represents about 60 per cent of manufacturing exports by Irish firms. Our success in this area is hinged on plants, whether as crops grown for direct consumption, as raw materials for other products or as animal feed for the meat and dairy sectors. Just recently our reliance on plants within the agri-food sector was emphasised by the fodder crisis. A longer than usual winter meant reduced grass growth and a need to provide an alternative food source for Ireland’s more than 6 million cattle. As the effects of climate change become more obvious on our weather patterns, this type of event may become more common.

The importance of plants only becomes truly obvious when crops fail

Perhaps then, the economic and societal importance of plants only becomes truly obvious when they fail us. Ireland’s history of famine due to late blight of potato in the mid 19^th Century had profound effects on Irish population levels and social history.

As well as an economic impact, plants also have an aesthetic quality which makes them good things to have around. A number of studies have reported the mental and physical health benefits of being exposed to plants and green spaces in general. One study, from the Netherlands, looked at 10,000 people’s general health and compared it to the amount of green space in their neighbourhood. A clear trend emerged: people living in areas with more plants, on average, experienced less symptoms of ill-health and perceived their own health to be better.

In a classic study conducted in the US in the 1980s, patients in a hospital ward with a view of a natural setting, including trees and other plants, recovered more quickly from surgery and took less pain-killing medication than patients with a window view of a brick wall.

Rather than taking them for granted, the role plants play in our lives needs to be recalled. The Irish writer Jonathan Swift once wrote: “Whoever makes two ears of corn, or two blades of grass grow where only one grew before, deserves better of mankind, and does more essential service to his country than the whole race of politicians put together”. With apologies to our local and national representative, I’d have to agree with Swift.

Today, May 18^th 2013, is International Fascination of Plants Day and events are taking place around the World to mark the importance of plants in our lives. More details on the website: www.plantday12.eu

Eoin Lettice is a lecturer in Plant Science at the School of Biological, Earth and Environmental Sciences (BEES) at University College Cork. He also writes the Communicate Science blog and you can follow him on twitter @blogscience