Planting non-native trees accelerates the release of carbon back into the atmosphere



native forest.

Lauren Waller and Warwick Allen, University of Canterbury

Large-scale reforestation projects such as New Zealand’s One Billion Trees programme are underway in many countries to help sequester carbon from the atmosphere.

But there is ongoing debate about whether to prioritise native or non-native plants to fight climate change. As our recent research shows, non-native plants often grow faster compared to native plants, but they also decompose faster and this helps to accelerate the release of 150% more carbon dioxide from the soil.

Our results highlight a challenging gap in our understanding of carbon cycling in newly planted or regenerating forests.

It is relatively easy to measure plant biomass (how quickly a plant grows) and to estimate how much carbon dioxide it has removed from the atmosphere. But measuring carbon release is more difficult because it involves complex interactions between the plant, plant-eating insects and soil microorganisms.

This lack of an integrated carbon cycling model that includes species interactions makes predictions for carbon budgeting exceedingly difficult.




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How non-native plants change the carbon cycle

There is uncertainty in our climate forecasting because we don’t fully understand how the factors that influence carbon cycling – the process in which carbon is both accumulated and lost by plants and soils – differ across ecosystems.

Carbon sequestration projects typically use fast-growing plant species that accumulate carbon in their tissues rapidly. Few projects focus on what goes on in the soil.

Non-native plants often accelerate carbon cycling. They usually have less dense tissues and can grow and incorporate carbon into their tissues faster than native plants. But they also decompose more readily, increasing carbon release back to the atmosphere.

Our research, recently published in the journal Science, shows that when non-native plants arrive in a new place, they establish new interactions with soil organisms. So far, research has mostly focused on how this resetting of interactions with soil microorganisms, herbivorous insects and other organisms helps exotic plants to invade a new place quickly, often overwhelming native species.

Invasive non-native plants have already become a major problem worldwide, and are changing the composition and function of entire ecosystems. But it is less clear how the interactions of invasive non-native plants with other organisms affect carbon cycling.




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Planting non-native trees releases more carbon

We established 160 experimental plant communities, with different combinations of native and non-native plants. We collected and reared herbivorous insects and created identical mixtures which we added to half of the plots.

We also cultured soil microorganisms to create two different soils that we split across the plant communities. One soil contained microorganisms familiar to the plants and another was unfamiliar.

Herbivorous insects and soil microorganisms feed on live and decaying plant tissue. Their ability to grow depends on the nutritional quality of that food. We found that non-native plants provided a better food source for herbivores compared with native plants – and that resulted in more plant-eating insects in communities dominated by non-native plants.

Similarly, exotic plants also raised the abundance of soil microorganisms involved in the rapid decomposition of plant material. This synergy of multiple organisms and interactions (fast-growing plants with less dense tissues, high herbivore abundance, and increased decomposition by soil microorganisms) means that more of the plant carbon is released back into the atmosphere.

In a practical sense, these soil treatments (soils with microorganisms familiar vs. unfamiliar to the plants) mimic the difference between reforestation (replanting an area) and afforestation (planting trees to create a new forest).

Reforested areas are typically replanted with native species that occurred there before, whereas afforested areas are planted with new species. Our results suggest planting non-native trees into soils with microorganisms they have never encountered (in other words, afforestation with non-native plants) may lead to more rapid release of carbon and undermine the effort to mitigate climate change.The Conversation

Lauren Waller, Postdoctoral Fellow and Warwick Allen, Postdoctoral fellow, University of Canterbury

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Don’t count your fish before they hatch: experts react to plans to release 2 million fish into the Murray Darling



Dean Lewins/AAP

Lee Baumgartner, Charles Sturt University; Jamin Forbes, Charles Sturt University, and Katie Doyle, Charles Sturt University

The New South Wales government plans to release two million native fish into rivers of the Murray-Darling Basin, in the largest breeding program of its kind in the state. But as the river system recovers from a string of mass fish deaths, caution is needed.

Having suitable breeding fish does not always guarantee millions of healthy offspring for restocking. And even if millions of young fish are released into the wild, increased fish populations in the long term are not assured.

For stocking to be successful, fish must be released into good quality water, with suitable habitat and lots of food. But these conditions have been quite rare in Murray Darling rivers over the past three years.

We research the impact of human activity on fish and aquatic systems and have studied many Australian fish restocking programs. So let’s take a closer look at the NSW government’s plans.

A mass fish kill at Menindee in northern NSW in January 2019 depleted Fisk stocks.
AAP

Success stories

According to the Sydney Morning Herald, the NSW restocking program involves releasing juvenile Murray cod, golden perch and silver perch into the Darling River downstream of Brewarrina, in northwestern NSW.

Other areas including the Lachlan, Murrumbidgee, Macquarie and Murray Rivers will reportedly also be restocked. These species and regions were among the hardest hit by recent fish kills.

Fish restocking is used worldwide to boost species after events such as fish kills, help threatened species recover, and increase populations of recreational fishing species.

Since the 1970s in the Murray-Darling river system, millions of fish have been bred in government and private hatcheries in spring each year. Young fish, called fingerlings, are usually released in the following summer and autumn.




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There have been success stories. For example, the endangered trout cod was restocked into the Ovens and Murrumbidgee Rivers between 1997 and 2006. Prior to the restocking program, the species was locally extinct. It’s now re-established in the Murrumbidgee River and no longer requires stocking to maintain the population.

In response to fish kills in 2010, the Edward-Wakool river system was restocked to help fish recover when natural spawning was expected to be low. And the threatened Murray hardyhead is now increasing in numbers thanks to a successful stocking program in the Lower Darling.

After recent fish kills in the Murray Darling, breeding fish known as “broodstock” were rescued from the river and taken to government and private hatcheries. Eventually, it was expected the rescued fish and their offspring would restock the rivers.

A Murray hardyhead after environment agencies transplanted a population of the endangered native fish.
North Central Catchment Management Authority

Words of caution

Fish hatchery managers rarely count their fish before they hatch. It’s quite a challenge to ensure adult fish develop viable eggs that are then fertilised at high rates.

Once hatched, larvae must be transported to ponds containing the right amount of plankton for food. The larvae must then avoid predatory birds, be kept free from disease, and grow at the right temperatures.




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When it comes to releasing the fish into the wild, careful decisions must be made about how many fish to release, where and when. Factors such as water temperature, pH and dissolved oxygen levels must be carefully assessed.

Introducing hatchery-reared fish into the wild does not always deliver dramatic improvements in fish numbers. Poor water quality, lack of food and slow adaptation to the wild can reduce survival rates.

In some parts of the Murray-Darling, restocking is likely to have slowed the decline in native fish numbers, although it has not stopped it altogether.

Address the root cause

Fish stocking decisions are sometimes motivated by economic reasons, such as boosting species sought by anglers who pay licence fees and support tourist industries. But stocking programs must also consider the underlying reasons for declining fish populations.

Swan Hill, home to a larger-than-life replica of the Murray cod, is just one river community that relies on anglers for tourism.
Flickr

Aside from poor water quality, fish in the Murray Darling are threatened by being sucked into irrigation systems, cold water pollution from dams, dams and weirs blocking migration paths and invasive fish species. These factors must be addressed alongside restocking.

Fish should not be released into areas with unsuitable habitat or water quality. The Darling River fish kills were caused by low oxygen levels, associated with drought and water extraction. These conditions could rapidly return if we have another hot, dry summer.

Stocking rivers with young fish is only one step. They must then grow to adults and successfully breed. So the restocking program must consider the entire fish life cycle, and be coupled with good river management.

The Murray Darling Basin Authority’s Native Fish Recovery Strategy includes management actions such as improving fish passage, delivering environmental flows, improving habitat, controlling invasive species and fish harvest restrictions. Funding the strategy’s implementation is a key next step.

Looking ahead

After recent rains, parts of the Murray Darling river system are now flowing for the first time in years. But some locals say the flows are only a trickle and more rain is urgently needed.

Higher than average rainfall is predicted between July and September. This will be needed for restocked fish to thrive. If the rain does not arrive, and other measures are not taken to improve the system’s health, then the restocking plans may be futile.




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The Conversation


Lee Baumgartner, Professor of Fisheries and River Management, Institute for Land, Water, and Society, Charles Sturt University; Jamin Forbes, Freshwater Ecologist, Charles Sturt University, and Katie Doyle, Freshwater Ecologist, Charles Sturt University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Arctic: Catastrophic Methane Release Coming


The link below is to an article reporting on the possible release of massive volumes of methane when the permafrost of the Arctic melts due to climate change and global warming.

For more visit:
http://inhabitat.com/new-report-finds-arctic-ice-melt-could-cost-70-trillion/

Regent Honeyeater: Captive-bred birds to be Released into Wild


The link below is to an article that reports on the planned release of captive-bred Regent Honeyeaters to boost wild population.

For more visit:
http://www.australiangeographic.com.au/journal/regent-honeyeater-population-gets-a-boost.htm

Article: Antarctic Climate Change – the Methane Connection


The link below is to an article that reports on the possibility of worsening climate change due to methane gas release from Antarctica as ice melts.

For more visit:
http://news.nationalgeographic.com/news/2012/08/120831-antarctica-methane-global-warming-science-environment/

Article: Artic – Methane Gas Release


The following link is to an article reporting on the release of methane gas in the Artic region due to climate change.

For more visit:
http://www.bbc.co.uk/news/science-environment-18120093