How ancient pollen can predict our future climate and what we need to do to conserve SA’s rich biome

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Ancient pollen grains found in sediment cores dating back thousands of years are helping scientists shed light on Earth’s past and future climates.

Dr Lynne Quick, a palynologist at Nelson Mandela University who is currently working on developing new paleoenvironmental recordings in southern Africa, says there is much more than pesky pollen and fungal spores wreaking havoc on people. allergic.

“Pollen is distinct in two ways. It has a unique shape depending on the plant it comes from and its outer layer consists of sporopollenin, which is chemically very stable and resistant to microbial rot. In fact, it is one of the most chemically inert organic compounds found on earth and is known as the “diamond of the plant world”. Sporopollenin preserves pollen grains in old deposits and sediments when almost all other organic material is reduced to unrecognizable components.

“When pollen is washed or blown into bodies of water and sinks, their walls remain intact, allowing them to remain preserved in the layers of sediment at the bottom of lakes, oceans and wetlands. Their unique shape allows us to identify which plant species were in abundance at the time of sediment deposition and through carbon dating we can determine the age of the fossilized pollen. Knowing what types of vegetation grew in an area allows us to make inferences about the climate at that time. This is because plants have bioclimatic niches, which means that they can only live and thrive under certain climatic and environmental conditions. Fossil pollen leaves an important imprint that can help us discover how our climate has changed over the millennia and what it might look like in the future, ”she explains.

Dr Lynne Quick and her team extract sediments from wetlands to analyze the pollen grains that have accumulated over time. This allows researchers to infer compositional changes in plant communities, thus creating vegetation stories.

There is a large body of work that covers the reconstruction of landscapes and environments using pollen evidence dating back thousands of years in different parts of South Africa. Most of the data generated by Dr Quick and other researchers are incorporated into climate and bioclimatic models as benchmarks for past vegetation changes, which can also aid in conservation management initiatives. environment.

She says that with future climate change, significant changes in the distribution of vegetation are likely to occur, which could threaten the high levels of species richness and endemism found in some of Africa’s unique biomes. from South.

These predictions are based on outputs from bioclimatic models that require the use of paleoecological data, such as fossil pollen records, to test the strength of the projections and validate the climate-vegetation assumptions inherent in these models.

The main regions of interest in South Africa include the fynbos (Western Cape and Eastern Cape), the Drakensberg (KwaZulu-Natal), the grasslands (central high plateau of South Africa and the interior areas of KwaZulu-Natal and Eastern Cape) and the savannah biomes (Free State, Northwest and Gauteng).

Morella pilulifera (Broadleaf Warberry)
While many allergenic trees, such as the plane tree, cypress and oak have been naturalized over several hundred years, aeolian pollen from the “Morella” or “Waxberry Tree” has been found in the fossil pollen records of the United States. southwest of Cape Town and Namaqualand as early as 66 million years ago.

Based on a 10,000-year-old fossil pollen, the Cape Floral Region was once abundant in both fynbos and forest, indicating plenty of rainfall and humidity, while future predictions suggest much climate. warmer and drier for the Western Cape.

“The extent of forest areas is expected to be reduced to isolated patches where conditions remain favorable, as well as potential reductions in the extent of the fynbos biome,” notes Dr. Quick. “In addition to the threat of climate change, the ongoing transformations of habitats (due to agricultural, seaside and urban development) and the rapid spread of exotic vegetation make the region particularly vulnerable to significant reductions in biodiversity. To limit the impact, conservation of the coastal lowlands of the fynbos biome should be a priority.

An image containing exterior, sky, tree, rock Description automatically generated
Scientists predict that a future hotter and drier climate could threaten the high levels of fynbos species currently found in the Western Cape.

The Drakensberg mountain range is also of immense ecological importance, due to its great plant biodiversity.

Ongoing high-altitude wetland pollen research by Dr Jemma Finch and Professor Trevor Hill at the University of KwaZulu-Natal has been used to reconstruct long-term vegetation dynamics and associated climate change. . “Their research indicates that the grasslands found in the area, which were traditionally considered secondary features of mountainous terrain – a type of degraded vegetation resulting from the clearing and burning of forests by prehistoric humans – are in fact an ancient type of vegetation. primary. “

The integration of pollen data with more traditional archaeological records which trace human occupation is particularly interesting in this region. Pollen records from the Drakensberg and its surroundings show that the grasslands have remained relatively stable in the past c. 5,000 years old, when forests were limited in their distribution, probably occupying fire-protected valleys and kloofs, as shown by the current grassland-forest mosaic.

Dr Quick says the long-term perspective provided by this pollen research highlights the conservation value of grasslands as an ancient and primary vegetation type dominating this important watershed. “While the climate continues to warm up throughout the 21st century, there are fears that mountain grassland species may be forced to respond by migrating up slopes, altering the makeup of these important grasslands, and affecting species that may not be able to keep up with the current rate of environmental change. “.

Analysis of pollen in the soil of the savannas of southern Africa shows variable changes in precipitation and warmer periods that have influenced vegetation changes over the past 6,000 years. Scientists say these landscapes could be compromised by the effects of CO2 fertilization, which will increase the growth rate of trees, allowing faster access to water in deeper soil layers at the expense of grasses. This effect is currently compounded by the intensification of illegal hunting of mega-herbivores, such as the white rhino, historically important in keeping the tree canopy open.

The loss of open, grassy landscapes has implications for grazers and other species of flora and fauna adapted to these environments and may be detrimental to wildlife tourism as it will reduce the potential for game viewing. According to Dr. Quick, paleoecological data, such as pollen surveys, can improve our understanding of ecological responses to natural and anthropogenic impacts and can help design appropriate restoration practices and stewardship programs. “Through this ecological lens of deep times, we can see that grasslands are not forms of degraded landscapes. Therefore, we need to carefully consider the implications of tree planting and forest expansion, as these efforts can undermine the provision of valuable ecosystem goods and services associated with grasslands. “

A tree in a Description field automatically generated with low confidence
The savannas of southern Africa can be compromised by the effects of CO2 fertilization, which are likely to increase the growth rate of trees at the expense of grasses.

She says studying old and current pollen is crucial because it will help inform future climate models and conservation efforts.

However, their funding remains problematic and hinders the work of scientists. More than R 1 million are needed each year to fund pollen monitoring.

The past 20 years of pollen monitoring in the Western Cape have provided crucial answers on the rate and extent of climate change. The researchers noticed fluctuations in the pollen seasons, which start earlier and end later than before. Above-average rainfall for Cape Town over the past two years has caused not only tree pollen levels to increase, but the number of allergenic trees has been above the 10-year average. Since 2011, higher grass pollen counts have also been recorded in October, when grass pollen generally peaks in Cape Town.

Professor Jonny Peter, head of allergology and clinical immunology at UCT Lung Institute, who also heads the South African Pollen Network (SAPNET), says that while national pollen surveillance has taken no magnitude that over the past three years, having access to data over a longer period of time will help predict long-term changes and how this is likely to influence plant life and aeroallergens in the future.

“Interest in studies of pollen season trends increased during the 1990s, when changes in temperature and pollen season parameters became more evident. Climate change alters the seasonality and intensity of pollen seasons, as well as the distribution of allergenic plants. Increasing CO2 concentrations and changes in air pollution affect the physiology of plants and their allergenicity, making hay fever one of the main health effects resulting from climate change.

“Predicting pollen is becoming increasingly important as general practitioners and allergists rely on data to provide effective patient care. Being aware of the high pollen count helps patients avoid exposure and encourages them to take preventative medication, ”he notes.

Through sponsorship from Clicks, Glenmark Pharmaceuticals, Dr Reddy’s and Johnson & Johnson, Novartis and Thermofischer Scientific, SAPNET is able to monitor pollen and mold spores in the coastal cities of Cape Town, Gqeberh and Durban, including areas inland from Johannesburg, Pretoria, Kimberley and Bloemfontein. The results are published weekly on https://pollencount.co.za.

For more information on Dr. Quik’s research, visit https://accp.mandela.ac.za/Palaeoecology-Lab.


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