The University of Southampton

Tag: plants

Could Climate Change STARVE us?

Posted on by Anonymous

The planet needs YOUR help!

We all have been alarmed and warned about rising sea temperatures, melting sea ice and glaciers, but the main problem is that we could describe them on and on.. Therefore, one of the greatest challenges the earth faces in this day and age is CLIMATE CHANGE.

A photo to show the loss of vegetation as a result of climate change (http://ayalim.org/israeli-plant-species-resistant-to-climate-change/)
A photo to show the loss of vegetation as a result of climate change  Available at:(http://ayalim.org/israeli-plant-species-resistant-to-climate-change/)

An unprecedented ↑ in atmospheric CO2 and temperature can shockingly lead to:

  • Species extinction
  • Collapsing ecosystems and food chains and as a result, foreseeable shortages of food and water to the increasing global population.

One of the toughest tasks this century, is predicting the response of plants to global climate change. Thus, what is essentially happening to our plants through this unpredictable change?

Many studies have observed:

Plants will thrive with an established elevation in CO2 and temperature…

  • As more CO2 = more fixation = more photosynthesis

Bisgrove and Hadley (2002) suggest that a “doubling in carbon dioxide level can increase plant growth by as much as 50%”

  • More heat = advanced growth and seed germination

 

HOWEVER…

Agriculture sustains almost all life-forms on Earth, meaning adverse conditions, can restrict crop plants in reaching their full genetic potential of producing a high yield (Anjum et al., 2014).

(1) Heat waves, extreme temperature events are projected to become more intense, more frequent and longer lasting to what is currently been observed in recent years (Hatfield and Prueger, 2015). Consequently, when a drought occurs where the levels of heat are extreme, the growth of a plant will rapidly decrease due to the high level of moisture loss. Furthermore, although water is essential for the functioning of virtually every plant on the planet, too much water (as a result of a storm… which we all can undeniably find exciting!) can in fact reduce the amount of oxygen in the soil, making a plant more susceptible to disease.

NOTE: Remember to stop and think, ‘this storm is not only damaging our plants, but in fact our livelihoods!’

(2) In addition, there is abundant evidence that in the long term, plants will begin to acclimate to a rise in CO2 levels. Therefore, the photosynthetic capacity becomes inhibited due to the plants being unable to utilise the additional carbohydrate that is accompanied with photosynthesis (Drake et al., 1997).

(3) Shockingly, crops of the future that are grown in a high- CO2 environment, will have decreases in the concentrations of zinc, iron and protein in grains of wheat, barley and rice (Myers et al., 2014) meaning the food in which we eat will be much less nutritious. Considering most people depend on these grains for their source of zinc and iron this can be detrimental to human health.

percentage
A graph to show the result in % reduction of nutrients from certain crops in an expected level of CO2 by 2050. (Source: NATURE)

 

If we continue to actively contribute to a world of increasing CO2 and temperature, not only are the plants on our Earth disturbed but if you stop and think: YOU yourself can be hugely affected.

A question of thought, who knows what this may cause to our future health and livelihoods?

 

 

References:

  • Anjum, N., Gill, S. and Gill, R. (2014). Plant adaptation to environmental change. 1st ed. Wallingford: CABI.
  • Bisgrove, R. and Hadley, P. (2002) Gardening in the Global Greenhouse: The Impacts of Climate Change on Gardens in the UK. Technical Report. Oxford: UKCIP.
  • Drake, B., Gonzalez-Meler, M. and Long, S. (1997). MORE EFFICIENT PLANTS: A Consequence of Rising Atmospheric CO2?. Annual Review of Plant Physiology and Plant Molecular Biology. 48(1), pp.609-639.
  • Hatfield, J. and Prueger, J. (2015). Temperature extremes: Effect on plant growth and development. Weather and Climate Extremes, 10, pp.4-10.
  • Myers, S., Zanobetti, A., Kloog, I., Huybers, P., Leakey, A., Bloom, A., Carlisle, E., Dietterich, L., Fitzgerald, G., Hasegawa, T., Holbrook, N., Nelson, R., Ottman, M., Raboy, V., Sakai, H., Sartor, K., Schwartz, J., Seneweera S., Tausz, M. and Usui, Y. (2014). Increasing CO2 threatens human nutrition. Nature, 510(7503), pp.139-142.

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A global invasion: Are all islands doomed?

Posted on by Cerridwen Richards
gannet
Islands: perfect breeding locations, or death traps?

Rats are definitely troublesome vermin. They raid our houses, they steal our food and they carry diseases. Not many of us would welcome a rat into our home, and a rat invasion is bad news everywhere, especially on islands.

Rats are non-native species to island ecosystems as seas and oceans act as barriers which hinder their dispersion. Unfortunately, by joining us for free boat trips, rats have successfully overcome this dispersion barrier, and incorporated themselves as unwelcome members of island communities. Today, rats have invaded up to 90% of the world’s islands (Towns et al., 2009). They are such effective invaders because they eat anything and everything, and can adapt quickly to new environments (Jones et al., 2008). The problem is that they change island communities and ecosystem functioning in the process…

No hope for seabirds?

Previously, islands were perfect habitats for nesting seabirds due to their lack of terrestrial predators (Latorre et al., 2013). Now, rat invasions are considered one of the largest threats to seabird breeding colonies (Jones et al., 2008). Once introduced, rats feed on the eggs and chicks of seabirds because they have no defensive strategies (Latorre et al., 2008). The result is the decline and local extinctions of seabird populations (Towns et al., 2009), but what is the consequence for island communities and ecosystems?

rats
Without defensive strategies, rats make easy meals out of seabird eggs and chicks

What if seabirds disappear from islands?

Seabirds provide key ecosystem services through two particular actions (Towns et al., 2009):

  1. Soil modification – By burrowing and nesting, seabirds change the soil environment for plants and     invertebrates.
  2. Soil fertilisation – Feeding at sea and depositing waste on land adds marine derived nutrients and minerals to the soil making it more productive.

 

On rat-invaded islands without the seabirds, these services are no longer provided. This has caused a change in the below-ground invertebrate community and the decline in numbers of several invertebrate groups including centipedes, ants, wasps and snails (Fukami et al., 2006; Towns et al., 2009).

Do rats only bring destruction?

rat-invasion
Rats predate on island-nesting seabirds resulting in the shift of above ground plant biomass (Fukami et al., 2006)

Although seabirds bring vital nutrients to the soil, they also cause considerable disturbance through:

  • Constantly changing the soil moisture by burrowing;
  • Trampling the soil and therefore preventing seedling growth;
  • Making the soil more acidic by creating waste (Fukami et al., 2006).

 

As mentioned before, rats feed on seabirds causing a negative indirect effects on the underground invertebrate community, but believe it, or not, they can actually have positive effects for islands. How? Well, it all occurs above ground. Introducing rats alleviates the three negative effects of seabirds on plants and soil (Fukami et al., 2006). The result is an increase in the amount and growth of ground-level plants on rat-invaded islands.

What can be done?

The effects of human-caused introductions of rats are undeniable. They reduce seabird populations, and indirectly influence above- and below-ground communities, ultimately resulting in changes to how island ecosystems function across the world (Fukami et al., 2006). Rat eradication programmes are vital if we want to restore island ecosystems and communities to their natural state.

 

References

Fukami, T., Wardle, D., Bellingham, P., Mulder, C., Towns, D., Yeates, G., Bonner, K., Durrett, M., Grant-Hoffman, M. and Williamson, W. (2006). Above- and below-ground impact of introduced predators in seabird-dominated island ecosystems. Ecology Letters, 9(12), pp.1299-1307.

Jones, H., Tershy, B., Zavaleta, E., Croll, D., Keitt, B., Finkelstein, M. and Howald, G. (2008). Severity of the effects of invasive rats on seabirds: a global review. Conservation Biology, 22(1), pp.16-26.

Latorre, L., Larrinaga, A. and Santamaria, L. (2013). Rats and seabirds: effects of egg size on predation risk and the potential of conditioned taste aversion as a mitigation method. PLoS ONE, 8(9), p.e76138.

Towns, D., Wardle, D., Mulder, C., Yeates, G., Fitzgerald, B., Parrish, G., Bellingham, P. and Bonner, K. (2008). Predation of seabirds by invasive rats: multiple indirect consequences for invertebrate communities. Oikos, 118(3), pp.420-430.

 

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Are plants on their way to killing us?

Posted on by Charlotte Alanine

          Have you ever noticed how much easier it is to breathe on a jog through a luscious park or a woodland compared to the inner city? This is because the air we breathe comes from the photosynthetic process plants provide. In this reaction, plants extract energy from carbon dioxide (CO2) combined with sunlight as well as other organic soil materials and release Oxygen (O2) as a by-product which we then benefit from.

 

         Photosynthesis under increasing CO2

          Each year since 1959, approximately half of the CO2 emissions we produce linger in our atmosphere (Le Quéré, et al., 2009). With atmospheric levels of CO2 on the rise as a result of our activities, the logical outcome would be that plants have additional CO2 to photosynthesise, allowing for more oxygen for us, right? Indeed, short-term increases have no negative impacts on photosynthesis. In fact, a study suggested they became more efficient at recycling CO2 (Besford, et al., 1990) as demonstrated in the positive feedback photosynthesis and growth of P.cathayana (Zhao, et al., 2012). However, under long-term carbon dioxide exposure, plants lost all photosynthetic gain (Besford, et al., 1990). Other studies have investigated the effects of increasing CO2 levels on plants and it has recently been found that previous models may have overestimated  the ability of plant “sinks” to make use of the additional human-related carbon. A “sink” is a location where carbon dioxide accumulates and is absorbed by plants much like running water down a sink.

 

From carbon sinks to carbon sources

        In 1991, Arp projected that plants in the field would not experience a decrease in photosynthetic abilities as a result of atmospheric CO2 increase. However, more recently in 2015, Wieder et al. reported that photosynthetic processes were limited by nutrient availability, in which phosphorus and nitrogen (Aranjuelo, et al., 2013) were the main limiting factors.

Figure 1. Modelling of changes in mean terrestrial carbon storage from an initial record 1860-1869 (top) to the 2100 projection with limited nitrogen and phosphorus (bottom). Source: Wieder et al. (2015)
Figure 1. Modelling of changes in mean terrestrial carbon storage from an initial record 1860-1869 (top) to the 2100 projection with limited nitrogen and phosphorus (bottom). Source: Wieder et al. (2015)

          In addition, their models projected that by 2100, plants which were once considered sinks may actually be turning into carbon sources (fig.1). This means they could be emitting more carbon than they absorb as a result of increasing carbon dioxide in the air in combination with the insufficient amounts of other organic materials (nitrogen, phosphorus, minerals, etc.) necessary for photosynthesis and consequently accelerating the rate of climate change which is bad news for us. Plants will essentially be slowly suffocating us as we rely on them for clean air.

 

 

 

A threat to food security

          Likewise, as a result of intensifying agriculture, soils are becoming increasingly eroded. For one, this means they are unable to store and process atmospheric carbon as efficiently and there is a lack of nutrients made available to plants (Lal, et al., 2008). This, coupled with the higher concentrations of CO2, poses a great threat to major crop plants such as oilseed rape (Franzaring, et al., 2011) and wheat (Uddling, et al., 2008). In laboratory studies, these crop plants tended to reduce the quality and quantity of their seeds in high concentrations of CO2.

          Emissions are not only posing a threat to a plant’s capacity to recycle air but also put our food security at risk.

References

Aranjuelo, I., Cabrerizo, P., Arrese-Igor, C. & Aparicio-Tejo, P., 2013. Pea plant responsiveness under elevated [CO2] is conditioned by the N source (N2 fixation versus NO3 – fertilization). Environmental and Experimental Botany, Volume 95, pp. 34-40.

Arp, W., 1991. Effects of source-sink relations on photosynthetic acclimation to elevated CO2. Plant, Cell and Environment, Volume 14, pp. 869-875.

Besford, R., Ludwig, L. & Withers, A., 1990. The Greenhouse Effect: Acclimation of Tomato Plants Growing in High CO2, Photosynthesis and Ribulose-1, 5-Bisphosphate Carboxylase Protein. Journal of Experimental Botany, 41(8), pp. 925-931.

Franzaring, J., Weller, S., Schmid, I. & Fangmeier, A., 2011. Growth, senescence and water use efficiency of spring oilseed rape (Brassica napus L. cv.Mozart) grown in a factorial combination of nitrogen supply and elevated CO2. Environmental and Experimental Botany, Volume 72, pp. 284-296.

Lal, R. et al., 2008. Soil erosion: a carbon sink or source?. Science, 319(5866), pp. 1040-1042.

Le Quéré, C. et al., 2009. Trends in the sources and sinks of carbon dioxide. Nature geoscience, 2(12), pp. 831-836.

Uddling, J. et al., 2008. Source-sink balance of wheat determines responsiveness of grain production to increased [CO2] and water supply. Agriculture, Ecosystems and Environment, Volume 127, pp. 215-222.

Wieder, W., Cleveland, C., Smith, W. & Todd-Brown, K., 2015. Future productivity and carbon storage limited by terrestrial nutrient availability. Nature, 8(6), pp. 441-445.

Zhao, H. et al., 2012. Sex-related and stage-dependent source-to-sink transition in Populus cathayana grown at elevated CO2 and elevated temperature. Tree Physiology, Volume 32, pp. 1325-1338.

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We need to change today, not the day after tomorrow…

Posted on by Alexandra Loveridge

The evidence for global environmental change is overwhelming. Increased levels of CO2 and other pollutants in the atmosphere cause constant and gradual increases in the average global temperature.  This is largely the fault of human activity through the burning of fossil fuels and the release of greenhouse gases. Carbon dioxide is long lived in our atmosphere and so these changes will continue happening for a long time even if we stop producing greenhouse gases.

img_0421
A tree line so straight it could have been drawn on with a ruler.

 

Have you ever gone to the mountains and wondered why there is a distinct sequence in the types of trees you see: deciduous, evergreen, then a well defined tree line above which there are rarely any trees?

This is because most plants can only live in very specific conditions. But global change will increase the amount of CO2 in the atmosphere, which warms the environment…

 

 

What does global environmental change mean for plants in the future?

 

 

 

Firstly, there will be a higher rate of photosynthesis under increased CO2. Rubisco, a key part of the photosynthetic process that fixes CO2, evolved at a time when there was a higher proportion of CO2 in the atmosphere. Under today’s much lower CO2 levels, this enzyme is far less efficient because Rubisco also fixes oxygen, wasting energy. So for plants, more CO2 in the environment means more photosynthesis, right?

Not necessarily true! Bowes (1993) suggested that at high levels of CO2 for a long time some plants may decrease the number of pores (stomata) that absorb CO2 on their leaves and the rate of photosynthesis may actually decrease. As well as this, changes to precipitation and nutrient supply may stop plants from reaching their full photosynthetic potential.

Secondly, rates of growth increase when plants are subjected to higher levels of CO2. Taylor et al. (1994) found that leaves and roots were bigger under higher levels of CO2 and also found that individual cells in the roots got larger too. However, some plants are already living on the edge of their physiological limits and cannot adapt. This may lead to some species dying out if they cannot adapt to the conditions quickly enough.

The UK: a future tropical paradise? Quite unlikely…

Finally plants will need to be hardier to withstand increased temperatures and occurrences of extreme weather events… Some plants have found a clever way to get around the warming problem. In the mountains, trees have gradually been moving higher up to avoid the warmer temperatures (Thuiller et al., 2005). As well as this, species such as mangroves are also shifting north (Field, 1995). This change in latitude is called a range shift. This doesn’t, however, mean that the future beaches around Britain will be warm and sunny and covered in palm trees unfortunately…

 

These changes will have a huge impact on society through reduced food security, changes to our water and power supplies, and may even impact on our health.

screenshot-2017-03-20-17-41-01
Its not the end of the world quite yet!

How do you think we can reduce these risks? What can people do to reduce their impact on the planet? Leave your thoughts and comments below!

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All photographs taken by Sophie Loveridge.

 

References

  • Monleon, V. and Lintz, H. (2015). Evidence of Tree Species’ Range Shifts in a Complex Landscape. PLOS ONE, 10(1), p.e0118069.
  • Field, C. (1995). Impact of expected climate change on mangroves. Hydrobiologia, 295(1-3), pp.75-81.
  • Bowes, G. (1993). Facing the Inevitable: Plants and Increasing Atmospheric CO2. Annual Review of Plant Physiology and Plant Molecular Biology, 44(1), pp.309-332.
  • Thuiller, W., Lavorel, S., Araujo, M., Sykes, M. and Prentice, I. (2005). Climate change threats to plant diversity in Europe. Proceedings of the National Academy of Sciences, 102(23), pp.8245-8250.
  • Taylor, G., Ranasinghe, S., Bosac, C., Gardner, S. and Ferris, R. (1994). Elevated CO2 and plant growth: cellular mechanisms and responses of whole plants. Journal of Experimental Botany, 45(Special_Issue), pp.1761-1774.


Plant Pores: How Carbon Dioxide Changes Stomata

Posted on by Alexanda Hewitt

 

Humans change the world around them. From farms to factories, that’s all on us. But what about a deeper level of change, happening to the parts of arguably our most important friends on this planet. The plants.

All types of plant have small holes, or pores, on their leaves called stomata. Each individual stoma is bound by a pair of cells called guard cells (see Figure 1), that help to control the uptake and release of gases (most importantly carbon dioxide (CO2) and water vapour) between the inside of the leaf and the atmosphere(1). This gas exchange as it were is regulated by the number of stomata that form on the leaf (the stomatal density) and by how open (the aperture) the stomatal pores are kept by the guard cells. The stomatal density and aperture are themselves influenced by environmental conditions such as light intensity and CO2 concentration(1).

Figure 1: A microscope image of a stoma. The pore is visible in the centre of the image, whilst the two guard cells (although they look like one circular cell surrounding the pore) can be seen either side of the pore(2).
Figure 1: A microscope image of a stoma. The pore is visible in the centre of the image, whilst the two guard cells (although they look like one circular cell surrounding the pore) can be seen either side of the pore(2).

CO2 concentration in the atmosphere is particularly important for modern day plants as although CO2 levels have fluctuated considerably over the last 400 million years(3), in the last 250 years they have risen by nearly 40%, a significant increase at a fast rate(4). Plants have thus had to go from living in some relatively low CO2 environments to living in a higher CO2 one(3). Experimental CO2 increases have shown to change the stomatal density by different amounts in different types of plant, but with an average of an 11% reduction with a doubling of the CO2 concentration, regardless of the starting density of the stomata(1). Furthermore, higher than normal CO2 levels in the atmosphere result in the closure of stomatal pores in plants(5).

These changes generally lead to a decrease (of between 21% and 40% in some studies(6)) in the amount of gas exchange between the plant and the atmosphere(1) but even this has other influences acting on it. The response to CO2 changes has been shown to be significantly stronger in younger trees, in non-evergreen trees and in trees that do not have enough water compared to those that do not have enough nutrients(6). This however, seems to be affected by the length of time that the leaves are in the higher than normal CO2 conditions with some leaves returning to a “normal” stomatal density after 2 years in a higher CO2 environment(7).

What does any of this actually do to the plant though? In some cases there has been an increased maximum rate of photosynthesis (the process by which plants make sugar from CO2 and water) at these higher CO2 levels(1). However, other studies have shown plants with the highest stomatal densities obtained the highest gas exchange rate and rate of photosynthesis, contrary to the previous results(8). Effectively we need more experiments to take place to get an accurate answer. What we do know is that we are changing the stomata on plants, be it for better or worse is yet to be decided.

 

References

  1. Hetherington AM, Woodward FI. The role of stomata in sensing and driving environmental change. Nature. 2003 Aug 21;424(6951):901-8.
  2. Ferry RJ. Stomata, Subsidiary Cells, and Implications. North American native orchid journal. 2008:168.
  3. Woodward FI. Do plants really need stomata?. Journal of Experimental Botany. 1998 Mar 1:471-80.
  4. Singh UB, Ahluwalia AS. Microalgae: a promising tool for carbon sequestration. Mitigation and Adaptation Strategies for Global Change. 2013 Jan 1;18(1):73-95.
  5. Engineer CB, Hashimoto-Sugimoto M, Negi J, Israelsson-Nordström M, Azoulay-Shemer T, Rappel WJ, Iba K, Schroeder JI. CO2 sensing and CO2 regulation of stomatal conductance: advances and open questions. Trends in plant science. 2016 Jan 31;21(1):16-30.
  6. Medlyn BE, Barton CV, Broadmeadow MS, Ceulemans R, De Angelis P, Forstreuter M, Freeman M, Jackson SB, Kellomäki S, Laitat E, Rey A. Stomatal conductance of forest species after long‐term exposure to elevated CO2 concentration: A synthesis. New Phytologist. 2001 Feb 1;149(2):247-64.
  7. Ainsworth EA, Rogers A. The response of photosynthesis and stomatal conductance to rising [CO2]: mechanisms and environmental interactions. Plant, cell & environment. 2007 Mar 1;30(3):258-70.
  8. Woodward FI, Lake JA, Quick WP. Stomatal development and CO2: ecological consequences. New Phytologist. 2002 Mar 1;153(3):477-84.

 

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