The Emerald Planet

"The Emerald Planet is a serious talking to about why plants must not be ignored.’ I agree with him that plants are grievously overlooked, because no life on earth would exist without them. It’s all either plants or something that eats them and this book basically explains plants’ place in earth’s history. It explains, for example, how the oxygen in the earth’s atmosphere came from plants, the role of plants and trees in the carbon cycle and, of course, we all understand that carbon has a role in controlling our climate nowadays. So, if you want to know about that then this is the book. Basically, the early earth had no oxygen in its atmosphere, and when the first life emerged, microbial single-cell stuff, oxygen was poisonous to it, because it interfered with important biochemical reactions. What plants did, or bacteria in the ocean did, was evolve a way of harnessing the carbon in sunlight and liberating oxygen in the process. Over time what happened is that oxygen built up in the atmosphere and you can see this in the fossil record. There are geological strata called red beds, iron-rich deposits. They are red because the iron rusted on exposure to oxygen, so there’s a point in earth history where you can see the oxygen appear because the iron in the soil rusted."

"Our story that has started in the ocean now spreads on to the land. What was critical was the shielding of the land surface from ultra-violet radiation. Yet living on land as David Beerling points out did not come easily. Plants had already learned to take carbon dioxide from the atmosphere and through photosynthesis using the green pigment chlorophyll and some neat chemistry use that with sunlight to incorporate carbon into its ‘skeleton’ and generate oxygen as a waste product. Plants also needed a way to break down minerals in the rocks to be able to take up essential elements. Eventually plants found a way to develop a mutually beneficial relationship with micorrhyzal fungi that aided this nutrient transfer. Plants also developed stomata, the gas exchange pores that regulated water loss and provided the conduit for carbon dioxide and oxygen. Plants also needed a more rigid skeleton and developed new materials such as lignin to strengthen the cellulosic cell walls of the plants. “plant life on land did not just change what was on the surface but developed a whole new rock cycle” However, life on land did not just change what was on the surface but developed a whole new rock cycle that enhanced erosion and hence supply of sediment and nutrients to the oceans and had a major impact upon the carbon cycle that in turn had a major impact upon the atmosphere. Beerling clearly shows that plants shaped the world in which we live and played a more important role on the evolution of our planet than is often acknowledged. Even today there are geologists who do not appreciate just how fundamental the greening of the planet was, and that is even more the case for the general public who, understandably, are more taken with animals such as dinosaurs rather than plants upon which we all ultimately depend. It was a desire to understand the early phase of how plants spread on to land and ultimately went on to form peats that were to become coal that I first thought of fire. It turns out that fire is a more significant force on Earth than many have appreciated and Beerling documents the early interest in the role that fire may have played in shaping our planet. Beerling emphasises just how much the Earth that we know today has been shaped by the plants that greened the land. While much is discussed about the blue planet he rightly takes us back to what is important for us – the emerald planet."