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The Earth's vegetation is changing at a faster rate today than it has over the last 18,000 years, and scientists think humans may be a big reason behind this.

Researchers have found that changes in biodiversity and ecosystems stabilised at around 4,000 years ago but it then began to change very quickly at a time when human civilisations grew leading to agriculture and deforestation.

The scientists involved in the study, published in the journal Science, think that these changes will continue, picking up pace over the coming decades, as a result of climate change brought about by humans.

Jack Williams, professor of geography at the University of Wisconsin-Madison in the US and one of the study authors, said: "This work suggests that 3,000 to 4,000 years ago, humans were already having an enormous impact on the world (and) that continues today."

How was the research carried out?

The team analysed more than 1,100 fossil pollen records from the Neotoma Paleoecology Database - which collects data on past ecosystems across every continent in the world apart from Antarctica.

They also looked at how the plant life on earth changed since the end of the last Ice Age - about 18,000 years ago - and how quickly the changes took place.

Earth's ecosystems underwent drastic changes at record pace at the end of the last Ice Age, according to the data, with plants growing rapidly over what had been frozen landscapes.

For most continents the changes peaked somewhere between 8,000 and 16,000 years ago, depending on the continent, and then became stable due to having a more consistent climate.

Sarah Ivory, an assistant professor of geosciences at Pennsylvania State University in the US, and also one of the study authors, said: ""Ecosystems were reorganising. Many of the megafauna (large or giant animals like mammoths) went away. It's hard to explain all that without climate."

But then 4,000 years ago more changes began in "a meteoric rise that continues today".

Sarah said: "During the later part of this period, there aren't major climate changes, so it is more likely human technology that is responsible."

The findings suggest that the changes seen over the last two centuries likely began thousands of years before - long before the Industrial Revolution in the mid-1700s and the rise of fossil fuels in the early 1900s.

They warn that as more land is used for activities like farming , and global temperatures rise due to greenhouse gases, they are likely to be many more changes to ecosystems to come which may yet again break new records.