Anthropogenic Transformation of the Terrestrial Biosphere: A Conclusion

Over my last two posts I have investigated the topic of anthropogenic transformation of the terrestrial biosphere. With so much information at hand I want to make sure that I wrap up this topic neatly and so this post will serve hopefully as a summary.

We have seen how humans alter ecosystems both by introducing novel processes (e.g. use of synthetic nitrogen fertilisers to increase productivity) and by altering pre-existing ones (e.g. genetically modifying crops to become resistant to herbicides and pesticides).

However, not all anthromes and biomes are affected equally by humans, as Ellis (2011) explores. It is reported that densely settled anthromes, such as towns and cities and cropland anthromes, incorporate the widest variety of novel ecosystem forms and processes and so are the most intensively transformed (Ellis, 2011). In these places pre-existing ecological patterns and processes have been shifted outside their natural range. Seminatural anthromes (such as hedgerows!) are transformed at lower levels of intensity. As you may have noticed from my previous posts, I have a great interest in seminatural anthromes. I think in this context their ecological importance is made really clear, and their role as refuges for non-agricultural species in increasingly transformed cropland anthromes is brought to light.

So the big question: Have human systems irreversibly transformed the terrestrial biosphere?

Well, if we take the most conservative view, then nearly one-third of the terrestrial biosphere has been transformed into anthromes in which pre-exisiting ecosystem forms and processes have been shifted beyond their natural range and so may now be considered to be novel (Ellis, 2011). 

Ellis (2011) concludes that the terrestrial biosphere is now predominantly anthropogenic. It is believed that it has been this way since the latter half of the twentieth century, when the transition from a terrestrial biosphere controlled by natural and biophysical processes to one that is controlled by human systems, was made. The sad news is (and I find this quite remarkable) if human populations were to disappear now, the global geological record of anthropogenic transformation of the terrestrial biosphere would persist – in other words: the changes are irreversible.

I really do find this exceptional and maybe that's why I have spent so much time on this topic. To consider the human system as something so powerful that is has strained the geological record is quite extraordinary. The news at the moment is dominated by stories of the flood risk that faces large parts of the UK, and the freezing ‘Arctic’ temperatures that North America is currently experiencing. These are reminders of the huge hold nature still has over us, and so as our ability to engineer the ecosystems increases exponentially, I think it’s important that we don’t forget the power of nature.

Is it really possible that human systems have greater control over ecosystem forms and processes than natural and biophysical processes? Source: The Telegraph

Anthropogenic Transformation of the Terrestrial Biosphere: A Novel Force?

Welcome back!

As promised, in today’s post I will be reviewing the idea that human systems represent a novel force of biospheric change, in other words one that is not duplicated in nature and one that is entirely unique.

In the Ellis paper, human development is organised into three major stages. I introduced these briefly in the last post but to refresh your memory here’s a quick run-through of what we’ve been getting up to over the past 2.5 million years…

Way, way back (around 2.5 million years ago in fact) we were organised into tribes. Stone tools were up-and-coming and fire was all range. We used these new gadgets to improve our hunting and gathering livelihoods. Our population stood at about several million and by 0.1 to 0.15 million years ago we had spread across most of the terrestrial biosphere.

Our palaeolithic ancestors began to use tools in hunting. Source: BBC

This all sounds harmless enough to me, however Koch & Barnosky (2006) suggest that the use of tools and fire to clear vegetation may be responsible (or at least in part responsible) for megafauna decline. Already we’re getting quite serious, and there’s not a fossil fuel in sight!

What we are really interested here is whether or not Palaeolithic human systems transformed ecosystems in ways that were entirely novel. Yes we used fire and yes there were megafaunal extinctions, however, Bowman (2009) says that these are both common effects of climate variation and so these processes were not unprecedented at the time. No evidence of novel transformation in the Palaeolithic era, but let’s move on to something more sophisticated!

Around 0.01Ma, we (Neolithic humans) learned to domesticate plants and animals for food. We were getting really handy with evermore powerful tools (in fact I believe the first B&Q was opened around 0.02Ma) and our ability to engineer the ecosystems was on the increase! Scientists believe that at this point our populations covered the vast majority of the terrestrial biosphere and by 1800 numbers had reached 900 million! (Ellis, 2011).

New research has found that Neolithic farmers used manure as a fertiliser on crops. Source: BBC

Any signs of any novel transformations by the Neolithic human system? Well, in contrast to what Koch & Barnosky(2006) said, Smith (2007) argues that the clearing of native vegetation and herbivores and their replacement by engineered ecosystems populated with domesticated plants and animals, does in fact represent an entirely novel biological process. I suppose when you think about it the evolution of many agricultural species is no longer a natural process, it is something that has come to be entirely controlled by humans.

And finally we progress to the industrial human system where we begin to burn fossil fuels for energy,  and we develop technologies for enhancing human survival rates, such as antibiotics and synthetic nitrogen fertilisers. Ellis(2011) identifies three novel biospheric processes that were introduced by the industrial human system:

1. The use of fossil fuel energy to replace biomass fuel and human and animal labour
2. The industrial synthesis of nitrogen fertilisers to increase productivity
3. The genetic engineering of species to increase productivity and yields

Genetically modified crops account for almost a quarter of all crops grown in the USA. Source: UNEP/GRID-Arendal

All of these novel processes serve to revolutionise our capacity to engineer the ecosystem and transform it.

From this three-stage model, it seems that human transformation of the terrestrial biosphere is consistent with the development of agriculture, which we first see during Neolithic times. Various technological advancements of the industrial era, for example the development of nitrogen fertilisers, certainly act to drive and intensify land-use changes.

However, it would be wrong of me to offer you this model without giving some kind of critique. Of course, anything that tries to explain such a complex process of events over a concise number of stages always runs the risk of oversimplification and I think that this may be the case here. However what it does do is it enables us to make a rough assessment of human systems as a force for transforming the terrestrial biosphere, and this is what I hope I’ve done here!

I think one further post is needed to neatly wrap up this topic so stay posted for my summary of anthropogenic transformation of the terrestrial biosphere.

P.s. I really recommend the Smith paper I mentioned above. It gives a really interesting insight into how early humans first gained the ability to transform the ecosystems and it talks in greater deal about processes of ecosystem engineering. 

Anthropogenic Transformation of the Terrestrial Biosphere: An Introduction

In today’s post I want to introduce the topic of anthropogenic transformation of the terrestrial biosphere. Over the next few posts I’m going to refer to Ellis (2011) and others in order to assess whether human populations have altered the terrestrial biosphere sufficiently enough to indicate that the Earth system has entered into a new geological epoch. I consider this to be an extremely important topic, well worthy of discussion as a change from natural, terrestrial biomes to ‘anthromes’ will bring about novel changes to many ecological patterns and processes and these will all have direct implications for Earth’s biodiversity.

See a decrease in seminatural and wild environments and an increase in dense settlements and villages since 1700. Source: Wired 

Human alteration of the terrestrial biosphere is not unprecedented and has in fact been significant for more than 8000 years. However, only in the past century has the majority of the biosphere been transformed into intensively used anthromes with predominantly novel anthropogenic ecological processes. There is strong evidence to show that humans have altered the Earth system sufficiently to indicate the emergence of a new geological epoch, one that scientists are calling the ‘Anthropocene’.

 

Human transformation of the terrestrial biosphere will leave a geological record that is significantly different from that of the Holocene or any prior epoch. Source: Plant Under Pressure

Some authors, including Jones et al. (1994), argue that any species with a large enough population will transform the ecosystems, simply by consuming the resources needed to sustain itself. However, scientists believe that there are profound differences in the way humans have been transforming the ecosystems, and some suggest that it is perhaps these differences that are responsible for the success of human society. Firstly, we are ecosystem engineers – just like beavers we are able to alter our environment. Secondly we are capable of using tools, and this makes the processes involved in ecosystem engineering all the more intense. Finally we are social creatures capable of collective action. Again this acts to increase our capacity to engineer the ecosystems (Ambrose, 2001).

Human development can be organised into three main stages:

1. The Palaeolithic human system – early humans were organised into tribes. Stone tools were first used around 2.5 million years ago and fire around 0.7-1.5 million years ago (Ellis, 2011) to improve hunting and gathering livelihoods.
2. The Neolithic human system – beginning around 0.01 million years ago. We see the first domestication of plants and animals here and humans began to use even more powerful tools for ecosystem engineering.
3. The Industrial human system – this is when we begin to use fossil fuels for energy. Industrial human systems are globally connected and the pace of social change is typically quite fast!

Illustration by Theodor de Bry (1591), showing indigenous Americans in Virginia cultivating maize fields. Some believe that the Anthropocene began with the rise of agriculture around 0.01Ma. Source: Recording the Anthropocene

So to develop this discussion further, in my next post  I'll explore the idea that these human systems are a force of biospheric change. In the mean time why not read the Ellis paper for yourself. It's a long one but I recommend it! It gives a good overview of many of the concepts of Global Environmental Change, including the Anthropocene and I found it particularly helpful in putting some of these complex concepts in context! 

Species game

Because it's the last week of term and Christmas is just around the corner I thought I'd post something fun for you all to be doing, to wind down from work!

This game allows players to try and guess how many identified species exist within each of the major kingdoms.

I played and I must admit I didn't do very well! See how well you can do and let me know. Perhaps this could be the next Candycrush...

Play now!

Glaciers and ice sheets as a biome

We had a lecture today about the cryosphere – the places on Earth where water is in its solid form – and glaciers and ice sheets were introduced as a biome. I found this idea particularly interesting and I was keen to discover a little bit more about it. So, I’ve done a bit of reading and here I’m going to share what I have found with you!

A biome is commonly defined as an area of the planet that can be classified according to the plants and animals that live in it. Temperature, soil, and the amount of light and water all help determine what life exists in a biome. The term itself is something I am familiar with but when I think of it I think of Tropical Rainforests and not glaciers and ice sheets.

When I think of the term 'biome' I think of Tropical Rainforests, not glaciers and ice sheets. Source: National Geographic

Alexandre M. Anesio and Johanna Laybourn-Parry argue that glaciers, ice sheets and the cryosphere are a biome uniquely dominated by microorganisms and active biogeochemical processes that have both local and global impacts. In their paper ‘Glaciers and ice sheets as a biome’, they say that it is time to recognise the cryosphere as one of Earth’s biomes.

The different habitats of the glacial biome

The ice surface

During the melting season, the presence of water provides habitats at the surface of the ice and snow. Distinct communities develop here comprising of species that are tolerant of low temperatures and able to overcome seasonal desiccation (Simon et al., 2009).

Subglacial environments
These habitats are a lot different from the ice surface environments for a number of reasons. Firstly they have a higher rock to water ratio that means the contact time between bedrock and water is much greater and secondly there is a lack of light, which tends to lead to the development of anoxic conditions. These environments dominated by heterotrophic and chemoautotrophic prokaryotes, as well as many fungal species.

Life within ice
Finally it is important to mention that a great deal of biological activity occurs within the ice itself. There are communities of algae, small animals and microbes all living inside the actual glaciers and ice sheets. This has been demonstrated by analysis of ice cores (e.g. Greenland Ice Project).

Ice core analysis has demonstrated that microbes and algae live inside the ice. Source: colorado.edu

Glaciers and ice sheets should be included as a biome
When I think of glaciers and ice sheets I don't picture much green nor many animals running around. However it is important to remember that these habitats support a high diversity of viruses and bacteria. Anesio and Laybourn-Parry (2012) suggest that this may be because a lot of microbial species are adapted to surviving and functioning under low temperature conditions. Despite this only a few studies have investigated the biodiversity of glacial habitats and where attempts have been made they have mostly been based on microscopic observations (e.g. Porazinska et al.,2004). 

The inclusion of glaciers and ice sheets as a biome with unique life adaptations would have wider implications for the conservation of these climate-sensitive ecosystems (Anesio and Laybourn-Parry, 2012). If these environments are not considered as one of Earth's biomes they may not receive the same conservation priority as other sensitive ecosystems. There will be global implications of this. For example the loss of biodiversity may lead to the loss of a pool of genes adapted to surviving and thriving in the cold. 

The loss of biodiversity from the cryosphere could lead to the loss of a pool of genes adapted to surviving in the cold. Source: travelsupermarket.com

In the water

The term is drawing to an end meaning that deadlines are looming. One such deadline that I am working towards at the moment is that of my independent study project. In this project I am investigating and evaluating a range of salinity reconstructions given by numerous proxies taken from a lake sediment core. This means that right now my life involves a lot of ‘palaeo[insert suffix here]’... I have gathered that you can affix pretty much anything on the end of ‘palaeo’ in order to study and make inferences about the past.

However, one such palaeo-combination that I only recently came across was ‘palaeobiodiversity’. I first encountered this paleo- in a paper by Adrian et al.(2009) in which the authors analyse the potential for lakes to act as ‘sentinels’ for climate change. The paper reports that the sensitivity of lakes to climate is well documented and that numerous studies have demonstrated that the physical, chemical, and biological lake properties respond rapidly to climate-related changes (ACIA, 2004). Other authors have suggested that what makes lakes so good at monitoring and recording the effects of climate change, is their high sensitivity to environmental changes as well as the fact that they conveniently integrate changes in the surrounding landscape and atmosphere (Carpenter et al., 2007).

Anyway, in the context of salinity variations in lake water I am afraid I hadn’t given much thought to how palaeolimnology (that’s the reconstruction of past lake environments) could be useful for studying biodiversity. So when I was introduced to palaeobiodiversity in that paper I thought that it would be interesting to learn more about this palaeo- (I’ll stop saying palaeo now, it gets annoying).

Irene Gregory-Eaves and Beatrix E. Beisner give a particularly useful contribution to the study of freshwater biology in their paper ‘Palaeolimnological insights for biodiversity science: an emerging field’. In this paper, the authors argue that palaeolimnology offers unique insights into biodiversity science, and the article highlights both its potential and limitation in providing further understanding of biodiversity dynamics.

What role will palaeolimnology play in the future of biodiversity science?

They write this article in the context of a growing need for scientists and policy makers to understand, predict and manage the consequences of rapid global declines in biodiversity (MillenniumAssessment, 2005). It could be argued that one of the greatest tools for prediction is the past, and I suppose that past trends are the underlying principle behind those fancy climate models developed by the likes of the IPCC (although I don’t know much about models and to be honest I don’t have much of a desire to venture into that section of the library so don’t quote me on this). With this in mind, as well as the fact that lakes make such good sentinels of climate change (Adrian et al.,2009), it makes perfect sense to me that palaeolimnology is used to understand and predict changes in global biodiversity.

As I said, the authors evaluate the role of palaeolimnology in biodiversity science. Palaeolimnology allows the researcher to focus on a single ecosystem, studying the way it changes over time (Gregory-Eaves and Beisner, 2011). This is a key advantage to anyone wishing to infer past changes in biodiversity in a particular area. Another benefit of using palaeolimnology to study biodiversity is the sheer timescale that can be studied. Investigators are able to quantify community responses to environmental changes over centuries, and even millennia! Clearly this would not be achieved by conducting any field-based survey typical of studies of biodiversity.

However, as is usually the case, for every benefit there is a limitation. Not all organisms preserve in sediments meaning that it is often difficult for investigators to find an identifiable remain to record. This is especially problematic for organisms that produce siliceous microfossils (e.g. diatoms) in lakes that are poor in silicate or are very alkaline (Stoermer et al.,  1985).

 

Diatom preservation is not as good in lakes that are poor in silicate

The application of palaeolimnological methods to the field of biodiversity science is a relatively new thing. However initial studies suggest that there is perhaps an exciting future to be had. For example, several studies are beginning to provide an insight into the drivers of community assembly and recovery. In this respect it seems likely that we’ll be seeing a lot more of palaeolimnology in biodiversity in the future!

NestWatch

Following on from last week's post, I wanted to highlight the importance of citizen science and the role it is playing in climate change science. The video below gives a good insight into one such citizen science project. NestWatch is a nationwide monitoring programme that has been designed by scientists at Cornell University. The aim of the project is to study the current condition of breeding birds and how breeding behaviour may be changing as a result of climate change and habitat degradation.