Can ecological research help cushion the blow of climate change?

Paul Ramsay working in the
mountains of Ecuador.
Photo: Paul Ramsay

Studies on high-altitude cushion and giant rosette plants offer insights into the effects of climate change in tropical mountains


by Chloe Turner

We are all aware of how human consumption is changing climatic conditions and affecting the Earth’s biodiversity. What you may not be aware of, however, is that species can sometimes be found in areas where you might not expect to find them if you base it solely on their environmental requirements. This is because of aspects of ecology, one being the interactions between species. The presence or absence of species can change factors such as light penetration and soil temperatures. A change in land use such as man-made fires or draining wetlands can alter the composition of ecosystems and result in species living in places that they would not otherwise inhabit.

A Plymouth university academic, Dr Paul Ramsay, has a keen interest in the distributions of organisms and their interactions with human land use. He has devoted 30 years of his career to the mountain ranges of the Andes, where he is unlocking some of the secrets that explain why species live where they do.  He hopes his work will help to halt some of the detrimental effects people have had on biodiversity in the Andes, and suggest ways that land managers can make better decisions for the future protection of biodiversity and ecosystem services.

Paul works on strange-looking giant rosette and cushion plants that live in the mountains, 3–5 km above sea level. “It’s nice to know that these quite rare and weird species still exist in this world”, he says, but adds, “The existence of these species tell us how evolution works, about the way biodiversity develops through time, how species interact and how all of these things have responded in the past to climate change.”

At the moment, he is studying thermal refuges of plants and animals at a fine scale (over centimetres) and unveiling key relationships between vegetation and soil temperature, and ideas for conservation in the face of future climate change.

Cushion plants at 3600m above sea level on the border
between Ecuador and Colombia in South America.
Photo: Paul Ramsay

Cushion plants are common in the Andes. They are often found in wetter areas, but also just below the snowline in rockier, more barren terrain. These cushion-dominated areas host some of the rarest and most specialized plants and animals. The microclimate they create is different to that of the soil and rocks around them. In this sense, cushion plants are considered to be ecosystem engineers, modifying the environment where they live. Although in the drier and sunnier parts of the Andes (in places like Chile), cushion plants are often warmer than their surroundings during the day, Paul's research in the cloudier Andes of Ecuador suggests that cushions are often cooler than their surroundings. In this way, they might provide a cooler refuge for some organisms as climate change kicks in around them.

In the past, Paul had explained the reason why similar species are found in wetlands and higher-altitude rocky areas as a simple case of a lack of competition, but these latest research results are leading him to other ideas about cushion plants as ecosystem engineers. There is also the chance that cushion plants could provide habitat for species that cannot survive the warming temperatures elsewhere on the mountain. This is would be especially good news for land managers because they could do something to help locally in the face of a global problem that is clearly out of their control.
  

Paola Garcia-Meneses and a Puya hamata plant,
which reveals this landscape’s past. Photo: Paul Ramsay.

Another strand of research has focused on the giant rosette plant, Puya hamata, which grows in the grasslands of these tropical mountains. Laboratory experiments showed that the seeds of this species only germinate when the soil temperature rises above 14°C. Strangely, the air temperature where the plant grows in the wild is on average only about 10°C. So how are these plants germinating in the areas they are found? The answer to this question is interesting and crucial for decisions about future management of these ecosystems. 

Tall, dense tussock grasses dominate the high-altitude grasslands of the Andes, and these plants block out the sun. In dense tussock grass, only about 1–2% of the soil surface receives direct sunlight, and with it the warmth of the tropical sun. The effect of this can be startling: within just 20 cm of distance, soil temperatures can vary from 5°C to 35°C. So, Puya is able to germinate only in places where direct sunlight hits the ground, the more open areas without dense vegetation shading it. 

A "seed’s-eye-view" of the sky in dense
vegetation. Photo: Paul Ramsay

This is a great example of how species interact with the environment, and gives clues about what might happen if things change in the future. From more detailed experimental work in the field, Paul has concluded that soil open to the sky, even though it is cloudy most of the time, experiences temperatures near the surface that are around 5°C warmer than soil shaded by vegetation. Compare these values with changes in temperature of about 5–6 °C for every 1 km of altitude, or a prediction of 2–3°C increase over the next 100 y because of climate change. It is clear that very local actions that change vegetation cover can make large differences to soil temperature, and that will affect the balance between species.

As an example, burning grasslands in the Andes is very common. It opens up the vegetation and lets light reach the soil. Not surprisingly, Puya loves the effects of burning, because it increases soil temperature and increases its own germination rate. Fires have allowed plants like Puya to grow higher up the mountains than they otherwise would. On the other hand, if fires are banned—as already the case in some protected areas—then a cooler soil temperature will lead to the loss of some species in the higher parts of their ranges. Again, it is an example of local actions leading to important changes in temperature for plants and animals.

This kind of research is fundamental because it shows that focusing too much on global issues can miss some very important local factors. Local land managers can change soil temperatures considerably by choosing to burn grasslands. Or, by draining wetlands, they can reduce the availability of cooler refuges for plants and animals that need them. Governments, protected areas, NGOs and farmers should work together and consider these local actions more carefully, in the context of longer term changes in climate and land use policies.



This article was originally submitted as a science communication assignment, for part of the BSc (Hons) Conservation Biology degree. It has been edited before posting here.