A genetically modified tree (GMt, GM tree, genetically engineered tree, GE tree or transgenic tree) is a tree whose

DNA Deoxyribonucleic acid (; DNA) is a polymer composed of two polynucleotide chains that coil around each other to form a double helix. The polymer carries genetic instructions for the development, functioning, growth and reproduction of al ...

has been modified using

genetic engineering Genetic engineering, also called genetic modification or genetic manipulation, is the modification and manipulation of an organism's genes using technology. It is a set of Genetic engineering techniques, technologies used to change the genet ...

techniques. In most cases the aim is to introduce a novel trait to the plant which does not occur naturally within the species. Examples include resistance to certain pests, diseases, environmental conditions, and

herbicide Herbicides (, ), also commonly known as weed killers, are substances used to control undesired plants, also known as weeds.EPA. February 201Pesticides Industry. Sales and Usage 2006 and 2007: Market Estimates. Summary in press releasMain page f ...

tolerance, or the alteration of

lignin Lignin is a class of complex organic polymers that form key structural materials in the support tissues of most plants. Lignins are particularly important in the formation of cell walls, especially in wood and bark, because they lend rigidit ...

levels in order to reduce

pulping Pulp is a fibrous lignocellulosic material prepared by chemically, semi-chemically, or mechanically isolating the cellulosic fibers of wood, fiber crops, waste paper, or rags. Mixed with water and other chemicals or plant-based additives, pul ...

costs. Genetically modified forest trees are not yet approved ("deregulated") for commercial use with the exception of insect-resistant poplar trees in China and one case of GM Eucalyptus in Brazil. Several genetically modified forest tree species are undergoing field trials for deregulation, and much of the research is being carried out by the

pulp and paper industry The pulp and paper industry comprises companies that use wood, specifically pulpwood, as raw material and produce pulp, paper, paperboard, and other cellulose-based products. Manufacturing process In the manufacturing process, pulp is intr ...

, primarily with the intention of increasing the productivity of existing tree stock. Certain genetically modified orchard tree species have been deregulated for commercial use in the United States including the

papaya The papaya (, ), papaw, () or pawpaw () is the plant species ''Carica papaya'', one of the 21 accepted species in the genus '' Carica'' of the family Caricaceae, and also the name of its fruit. It was first domesticated in Mesoamerica, within ...

and

plum A plum is a fruit of some species in Prunus subg. Prunus, ''Prunus'' subg. ''Prunus'.'' Dried plums are often called prunes, though in the United States they may be labeled as 'dried plums', especially during the 21st century. Plums are ...

. The development, testing and use of GM trees remains at an early stage in comparison to GM crops.

Research

Research into genetically modified trees has been ongoing since 1988. Concerns surrounding the

biosafety Biosafety is the prevention of large-scale loss of biological integrity, focusing both on ecology and human health. These prevention mechanisms include the conduction of regular reviews of biosafety in laboratory settings, as well as strict guidel ...

implications of releasing genetically modified trees into the wild have held back regulatory approval of GM forest trees. This concern is exemplified in the

Convention on Biological Diversity The Convention on Biological Diversity (CBD), known informally as the Biodiversity Convention, is a multilateral treaty. The Convention has three main goals: the conservation of biological diversity (or biodiversity); the sustainable use of its ...

's stance: A precondition for further commercialization of GM forest trees is likely to be their complete sterility. Plantation trees remain phenotypically similar to their wild cousins in that most are the product of no more than three generations of

artificial selection Selective breeding (also called artificial selection) is the process by which humans use animal breeding and plant breeding to selectively develop particular phenotypic traits (characteristics) by choosing which typically animal or plant ...

, therefore, the risk of

transgene A transgene is a gene that has been transferred naturally, or by any of a number of genetic engineering techniques, from one organism to another. The introduction of a transgene, in a process known as transgenesis, has the potential to change the ...

escape by

pollination Pollination is the transfer of pollen from an anther of a plant to the stigma (botany), stigma of a plant, later enabling fertilisation and the production of seeds. Pollinating agents can be animals such as insects, for example bees, beetles or bu ...

with compatible wild species is high. One of the most credible science-based concerns with GM trees is their potential for wide dispersal of

seed In botany, a seed is a plant structure containing an embryo and stored nutrients in a protective coat called a ''testa''. More generally, the term "seed" means anything that can be Sowing, sown, which may include seed and husk or tuber. Seeds ...

and

pollen Pollen is a powdery substance produced by most types of flowers of seed plants for the purpose of sexual reproduction. It consists of pollen grains (highly reduced Gametophyte#Heterospory, microgametophytes), which produce male gametes (sperm ...

. The fact that pine pollen travels long distances is well established, moving up to 3,000 kilometers from its source. Additionally, many tree species reproduce for a long time before being harvested. In combination these factors have led some to believe that GM trees are worthy of special environmental considerations over GM crops. Ensuring sterility for GM trees has proven elusive, but efforts are being made. While tree geneticist Steve Strauss predicted that complete containment might be possible by 2020, many questions remain.

Proposed uses

GM trees under experimental development have been modified with traits intended to provide benefit to industry, foresters or consumers. Due to high regulatory and research costs, the majority of genetically modified trees in

silviculture Silviculture is the practice of controlling the growth, composition/structure, as well as quality of forests to meet values and needs, specifically timber production. The name comes from the Latin ('forest') and ('growing'). The study of forests ...

consist of plantation trees, such as

eucalyptus ''Eucalyptus'' () is a genus of more than 700 species of flowering plants in the family Myrtaceae. Most species of ''Eucalyptus'' are trees, often Mallee (habit), mallees, and a few are shrubs. Along with several other genera in the tribe Eucalyp ...

, poplar, and

pine A pine is any conifer tree or shrub in the genus ''Pinus'' () of the family Pinaceae. ''Pinus'' is the sole genus in the subfamily Pinoideae. ''World Flora Online'' accepts 134 species-rank taxa (119 species and 15 nothospecies) of pines as cu ...

Lignin alteration

Several companies and organizations (including ArborGen, GLBRC, ...) in the pulp and paper industry are interested in utilizing GM technology to alter the

content of plantation trees (particularly

and poplar trees). It is estimated that reducing lignin in plantation trees by genetic modification could reduce pulping costs by up to $15 per cubic metre. Lignin removal from wood fibres conventionally relies on costly and environmentally hazardous chemicals. By developing low-lignin GM trees it is hoped that pulping and bleaching processes will require fewer inputs, therefore, mills supplied by low-lignin GM trees may have a reduced impact on their surrounding

ecosystems An ecosystem (or ecological system) is a system formed by Organism, organisms in interaction with their Biophysical environment, environment. The Biotic material, biotic and abiotic components are linked together through nutrient cycles and en ...

and communities. However, it is argued that reductions in lignin may compromise the structural integrity of the plant, thereby making it more susceptible to wind, snow,

pathogen In biology, a pathogen (, "suffering", "passion" and , "producer of"), in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a Germ theory of d ...

s and disease, which could necessitate

pesticide Pesticides are substances that are used to control pests. They include herbicides, insecticides, nematicides, fungicides, and many others (see table). The most common of these are herbicides, which account for approximately 50% of all p ...

use exceeding that on traditional plantations. This has proven correct, and an alternative approach followed by the University of Columbia was developed. This approach was to introduce chemically labile linkages instead (by inserting a gene from the plant '' Angelica sinensis''), which allows the lignin to break down much more easy. Due to this new approach, the lignin from the trees not only easily breaks apart when treated with a mild base at temperatures of 100 degrees C, but the trees also maintained their growth potential and strength.

Frost tolerance

Genetic modification can allow trees to cope with

abiotic stress Abiotic stress is the negative impact of non-living factors on the living organisms in a specific environment. The non-living variable must influence the environment beyond its normal range of variation to adversely affect the population performan ...

es such that their geographic range is broadened. Freeze-tolerant GM eucalyptus trees for use in southern US plantations are currently being tested in open air sites with such an objective in mind. ArborGen, a tree biotechnology company and joint venture of pulp and paper firms Rubicon (New Zealand),

MeadWestvaco MeadWestvaco Corporation was an American Packaging and labeling, packaging company based in Richmond, Virginia, Richmond, Virginia. It had approximately 23,000 employees. In February 2006, it moved its corporate headquarters to Richmond. In March ...

(US) and International Paper (US) is leading this research. Until now the cultivation of eucalyptus has only been possible on the southern tip of Florida, freeze-tolerance would substantially extend the cultivation range northwards.

Reduced vigour

Orchard trees require a

rootstock A rootstock is part of a plant, often an underground part, from which new above-ground growth can be produced. It could also be described as a stem with a well developed root system, to which a bud from another plant is grafted. It can refer to ...

with reduced vigour to allow them to remain small. Genetic modification could allow the elimination of the rootstock, by making the tree less vigorous, hence reducing its height when fully mature. Research is being done into which genes are responsible for the vigour in orchard trees (such as apples, pears, ...).

Accelerated growth

In Brazil, field trials of fast growing GM eucalyptus are currently underway, they were set to conclude in 2015–2016 with commercialization to result. ''FuturaGene'', a biotechnology company owned by Suzano, a Brazilian pulp and paper company, has been leading this research. Stanley Hirsch, chief executive of FuturaGene has stated: "Our trees grow faster and thicker. We are ahead of everyone. We have shown we can increase the yields and growth rates of trees more than anything grown by traditional breeding." The company is looking to reduce harvest cycles from 7 to 5.5 years with 20-30% more mass than conventional eucalyptus. There is concern that such objectives may further exacerbate the negative impacts of plantation forestry. Increased water and soil nutrient demand from faster growing species may lead to irrecoverable losses in site productivity and further impinge upon neighbouring communities and ecosystems. Researchers at the University of Manchester's Faculty of Life Sciences modified two genes in poplar trees, called PXY and CLE, which are responsible for the rate of cell division in tree trunks. As a result, the trees are growing twice as fast as normal, and also end up being taller, wider and with more leaves.

Disease resistance

Ecologically motivated research into genetic modification is underway. There are ongoing schemes that aim to foster disease resistance in trees such as the

American chestnut The American chestnut (''Castanea dentata'') is a large, fast-growing deciduous tree of the Fagaceae, beech family native to eastern North America. As is true of all species in the genus ''Chestnut, Castanea'', the American chestnut produces Bur ...

(see

Chestnut blight The pathogenic fungus ''Cryphonectria parasitica'' (formerly ''Endothia parasitica'') is a member of the Ascomycota (sac fungi). This necrotrophic fungus is native to East Asia and South East Asia and was introduced into Europe and North America ...

) and the English elm (see Dutch elm disease) for the purpose of their reintroduction to the wild. Specific diseases have reduced the populations of these emblematic species to the extent that they are mostly lost in the wild. Genetic modification is being pursued concurrently with traditional breeding techniques in an attempt to endow these species with disease resistance.

Current uses

Poplars in China

In 2002 China's State Forestry Administration approved GM poplar trees for commercial use. Subsequently, 1.4 million Bt (

insecticide Insecticides are pesticides used to kill insects. They include ovicides and larvicides used against insect eggs and larvae, respectively. The major use of insecticides is in agriculture, but they are also used in home and garden settings, i ...

) producing GM poplars were planted in China. They were planted both for their

wood Wood is a structural tissue/material found as xylem in the stems and roots of trees and other woody plants. It is an organic materiala natural composite of cellulosic fibers that are strong in tension and embedded in a matrix of lignin t ...

and as part of China's 'Green Wall' project, which aims to impede

desertification Desertification is a type of gradual land degradation of Soil fertility, fertile land into arid desert due to a combination of natural processes and human activities. The immediate cause of desertification is the loss of most vegetation. This i ...

. Reports indicate that the GM poplars have spread beyond the area of original planting and that contamination of native poplars with the Bt gene is occurring. There is concern with these developments, particularly because the pesticide producing trait may impart a positive selective advantage on the poplar, allowing it a high level of invasiveness.

Living Carbon in the USA

Living Carbon, an American biotechnology company founded in 2019, has developed genetically engineered hybrid poplar trees aimed at enhancing carbon sequestration. These trees have been modified to improve photosynthetic efficiency, enabling them to capture more carbon dioxide (CO₂) and produce greater woody biomass than conventional trees. Living Carbon’s mission is to leverage technology to combat climate change while promoting biodiversity and restoring degraded ecosystems.

Development and Deployment

Living Carbon’s genetically modified trees were first planted in a bottomland forest in Georgia, USA, in February 2023. Early field trials indicated that these trees achieved a 53% increase in above-ground biomass compared to control groups, enabling them to absorb 27% more carbon. The company generates revenue by selling carbon credits derived from these forests to individuals and businesses seeking to offset greenhouse gas emissions.

Benefits and Potential

Supporters of Living Carbon’s approach highlight its potential to contribute to global climate solutions, particularly if deployed on a large scale. The modified trees are targeted for use in afforestation and reforestation projects on degraded land, where they can aid in carbon capture and ecosystem restoration without displacing native species. These projects also aim to enhance biodiversity while addressing environmental degradation.

Controversies and Challenges

The deployment of genetically modified trees has been met with skepticism. Critics, including some forestry and genetic experts, question whether the trees will meet carbon absorption expectations outside controlled laboratory settings. Concerns have also been raised about the potential ecological risks, such as the unintended spread of genetically modified traits to wild tree populations, which could disrupt native ecosystems. Maddie Hall, co-founder of Living Carbon, has addressed these concerns, emphasizing the urgency of climate action and the limitations of waiting for natural evolutionary processes to improve tree resilience. However, experts note that achieving success in lab or greenhouse trials does not guarantee similar outcomes in complex, natural environments.

References

{{Horticulture and gardening Genetically modified organisms Environmental issues with forests Trees