World is getting ‘greener and bushier' according to U of G study

Ecological changes are happening at a great rate globally, and the world is getting ‘greener and bushier' according to a study led by Andrew MacDougall, a professor in the College of Biological Science at the University of Guelph. 

"I thought grasslands are probably getting dryer and droughty and are probably more susceptible to not producing grass at all. That was my thought, but that wasn't the case at all," MacDougall said. 

"In fact, 56 per cent of the grasslands are actually greener and bushier. And that, was totally unexpected." 

Grasslands, which cover about a quarter of the Earth’s land surface, are essential for supporting biodiversity, maintaining soil health and regulating carbon storage. 

MacDougall's interest was sparked from previous research, after German scientist, who in 1917, climbed a mountainside in Sweden to collect vegetation data.

"This particular fellow climbed the same mountain in Sweden for three years. Every five days he went up for three years and looked at what species were flowering and what species were present, which is a remarkably modern type study, and with a thorough level of scientific detail," MacDougall said.

Researchers from the University of Guelph returned to the same place, 100 years later, to find that surprisingly, nothing had changed. 

"What this created for us was a time machine. We can go back and see what he saw and then repeat exactly the same procedures, which we did, starting in 2017, to see how different things are," MacDougall said. 

In a study recently published in Nature Ecology & Evolution, MacDougall assembled a team of more than 80 grassland researchers worldwide. 

In this study, researchers collected data for 84 grassland sites since the 1980s, combining decades of remote satellite data with on-the-ground field observations, a first for grasslands research. 

They found that grasslands are experiencing sharp increases or declines in plant production depending on location, climate and local conditions. 

Findings also show that grasslands have not followed 'uniform rules' in response to global climate change. Many places, like the mountainside in Sweden, are stable and resistant to change. But worldwide, grasslands are undergoing dramatic changes.

Variability in grassland biomass appears to be related to hotter temperatures, changes in precipitation and longer growing seasons. The study found the average global growing season increased by an average of nine days since the 1980s. 

"But there were no species that disappeared. There were some tree line shifts, of about 150 metres. But 150 metres over 100 years, is basically, about one metre a year," MacDougall said.

"That's still significant but it's not very much compared to what we might have seen, and given the height of this mountain, it would take another 1,000 years for the trees to reach the peak essentially. So, there weren't as many changes as we thought. So, that's how the study started."

The study on the Swedish mountain was largely relating to phenology, the study of timing and cyclical patterns of events in the natural world. 

"That's the focus we took for the 80 researcher global grass study. When do the grasses get green in the spring, and when do they get brown in the fall?" MacDougall said. 

"There is satellite data, almost 40 years of annual measurements of greening and browning in global grasslands. We use that to test the same sort of timing of flowering and senescence for the mountain. But in this case, we did it for global grasslands. And again, what we saw was not what we would have expected. There was a lot of variability." 

If biomass is declining in some grasslands and increasing in others, that could lead to changes in food production around the world, with some areas more vulnerable to climate change.  

"With climate change, a question is what is going to happen to that food and how secure is it?" MacDougall said

“Grasslands are a critical ecosystem for agriculture. Grasslands support dairy and beef. There are 850 million people on the planet that have a direct economic or dietary connection to grasslands, so, they are critically important for food security."

MacDougall said if there is a green house where it's warmer, and everything is being watered, it will get bushier.

"And that's one of the things that's happening. It's getting hotter everywhere, but it's not getting dry everywhere," he said. 

"If you take a hot versus cold shower, only the the hot shower steams up your mirror because hotter air holds more water. That's exactly what's happening in a lot of places in the world, especially in the temperate northern hemisphere. It's getting warmer, but also moistier. Guelph is getting more rainfall than we did in the 1960's."

Despite lengthened growing seasons, some sites, especially in the Arctic, showed no change in biomass at all. 

MacDougall plans to continue to monitor how grasslands respond to environmental change globally, and further expand research in underrepresented areas in Africa and Asia.

He says this collaboration allowed for more accurate assessments at sites all around the world. 

"Personally, I think the biggest take home message from the study is how unexpected the results were," MacDougall said. 

“The collaborative nature of this project gives us the powerful data we need to test these complex questions."