A new environmental threat looms over the Earth: scientists warn of "ticking time bombs" around the world

Yulia PoteriankoNews
Some artificially introduced ornamental species can cause many problems over time. Source: Created with the help of AI

Anyone who has ever fought weeds in a garden knows what problems can be caused by plants that replace garden crops. This means that they also know what damage can be caused by invasive plant species, i.e. those introduced from other ecosystems that begin to compete with native species for ecological niches and resources.

Scientists argue that this problem can be even more serious, as invasive species can stay dormant for a long time before they begin to spread rapidly and cause damage. According to SciTechDaily, it can take decades or even centuries, which is why botanists call such plants "time bombs."

The alarm was caused by the results of a large analysis conducted by botanists at the University of California, Davis, which were published in the journal Nature Ecology and Evolution. The scientists examined more than 5,700 species of invasive plants in nine regions of the world. This is the most comprehensive analysis of its kind to date.

According to Mohsen Mesgaran, senior author and associate professor of botany at the University of California, Davis, the longer the dormancy period of invasive species, the more likely people are to ignore the danger. And this ultimately contributes to the transformation of a local problem into a serious invasive threat.

How long do dormant periods last?

As the international team of researchers found, almost a third of the plants analyzed had a delay period between introduction and rapid spread. The average period was 40 years. The record holder here was the sycamore, which had been dormant in the UK for 320 years.

Plantago lanceolata, or lanceolate plantain, is an illustrative species among the studied ones. It demonstrated the longest dormancy period in the United States. The plant, which is harmful to livestock and local flora, was introduced to North America in 1822. Now it is very widespread in the country. Meanwhile, Theophrastus abutilus is known to remain dormant for 50 years before it grows, threatening corn, soybeans, and other crops as it absorbs water and nutrients.

There are two ways to introduce non-native plant species. They are introduced accidentally or intentionally for medicinal, ornamental, agricultural, and other purposes. For example, in California, about 65% of invasive plants were deliberately introduced. Now, with the development of transportation, tourism, and trade, the number of accidentally introduced plants may also begin to increase.

Global herbaria of invasive species

While studying invasive species, researchers have compiled them into separate lists for Australia, the United Kingdom, Ireland, Japan, New Zealand, Madagascar, South Africa, Japan, and the United States. They published the digitized herbaria online, with data on the place and time of the species' observation.

They then studied the trends to determine whether the plants were dormant and, if so, for how long. Time-series analysis was used to identify periods of delay, followed by a second analysis comparing the climate during the dormant and spreading phases.

For some species that have invaded different regions, the dormancy periods differed depending on the location. According to Mesgaran, in 90% of cases, climatic conditions changed during the spread of the species, suggesting that the plants were waiting for the right conditions or adapted to survive in an environment that was once unsuitable for them.

Planning for the future

Knowing what problems the spread of invasive species may cause in the future is key to combating them and their spread, as well as the economic damage they can cause. "The problem is that most of the models we have for risk assessment to see if species will be invasive and a pest problem in the future don't take into account this lag phase or dormant phase," Mesgaran explained.

The team of scientists plans that the next steps in the study of this environmental problem should be to study the natural climate of invasive species compared to conditions in new places.

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