Tuesday July 31, 2012
Barcode for trees to curb illegal logging
BY NATALIE HENG
DNA profiling for trees will, one day, be used to curb illegal logging.
DEOXYRIBONUCLEIC acid, otherwise known as DNA, is nature’s barcode. It is inherent in nearly every cell in every organism, and could just be our answer to curbing illegal timber trade.
It might sound like science fiction or something out of an alternative CSI episode where investigators track down trees instead of killers, but DNA fingerprinting for trees based on technologies routinely used in criminal forensics holds much promise in the field of international enforcement.
In fact, these tools are prime candidates for putting a spanner on illegal logging – an industry which has devastating consequences for biodiversity, ecosystems and national economies alike.
To understand how this is possible, you need to think of DNA as a code. Genes in specific sequences translate into a variety of proteins which do most of the work in cells (structure, function, and regulation of the body’s tissues and organs, for example).
A good analogy put forward by evolutionary biologist Richard Dawkins is to think of genes as instructions in a cooking recipe. The instructions “collaborate” in the cookery process to culminate in a dish. Genes are expressed in a similarly collaborative fashion, but result in developmental processes which culminate in a body, be it human, fly or tree.
Dr Lee Soon Leong specialises in the DNA found in trees. He wades through peat swamps and treks through isolated forests to expand his collection of tree DNA samples, which he studies at the genetics laboratory at Forestry Research Institute Malaysia (FRIM).
In this leafy hub of scientific activity hidden away from the dusty streets of Kepong, Kuala Lumpur, Lee heads the genetics laboratory. In recent years, his team has been engaged in research which has important implications for prosecutors trying to bring illegally logged timber cases to court.
To understand this work, however, we first need to understand a highly interesting and useful feature of DNA – some sequences are highly conserved, whilst others are more variable.
Chloroplast genes which code for proteins involved in photosynthesis, for example, perform an important function that green plants cannot do without – allowing green plants to use energy from sunlight to synthesise food out of carbon dioxide and water. The DNA in these gene sequences are therefore highly conserved, and are likely to be very consistent between individuals of the same plant species.
Not all DNA sequences actually code for genes, however, and within these intergenic regions, harmless mutations which do not pose any disadvantage will often occur, and be passed on to subsequent generations. In this way, sequence changes can clock up along these segments, so the DNA profiles of specific intergenic regions in a distantly related group of trees will be increasingly more divergent from those of their founding population. This feature makes DNA profiling the perfect tool for shedding light on the murky routes of illegal timber trade, which is often obscured by log laundering.
Dodgy paperwork is just one of the methods companies use to disguise the origin and species of timber, effectively “legalising” logs that have come from an illegal source.
When you consider how advanced the world has become – increasingly powerful and advanced technologies being made to members of the public through smartphones, for example – it is surprising just how rudimentary our global timber trade tracking system is. The main checks that occur rely on an examination of externally applied, and easily manipulated, marks such as ink, metal bands and tags. These are cross-checked against paper documents, which can be falsified.
It is hard to blame customs officials. After all, a block of wood is, to the average person, a block of wood. Shipments of processed logs all pretty much look the same when you’re not trained in wood anatomy, which is currently the standard method used in log identification.
Even then, a timber package suspicious enough to warrant checking is subject to some disadvantages – important timber tree species are not necessarily visually distinguishable from similar species in the sawn form. All these are serious problems when it comes to the mislabelling of trade-restricted or endangered species of wood for laundering purposes.
The barcode of life
Illegal loggers might be able to mess with the paper system but they cannot mess with DNA. It is a unique property inherent in trees, and present in almost every cell within a solid wood product. It is the differences in variability across the genome that has allowed scientists like Lee to play detective, taking unknown wood samples, and tracing their origins using specific DNA sequences or “DNA markers”. Highly conserved DNA markers that are consistent within a species can be used as “barcodes” for species identification, he explains.
Since their project began in 2010, Lee’s team has amassed barcodes for half of Malaysia’s 408 commercially valuable timber species. The database of barcodes can be used for rapid identification of wood species used in heavy construction and furniture manufacturing. There is also potential implication in conservation as the barcodes can be used to assess plant biodiversity.
Whilst the highly conserved barcodes can be used for timber species identification, intergenic markers can be used to track geographical origins. Closely related trees located within the same timber concession might share common marker sequences, but the further you go, the more variation you will find within those markers. This effectively enables scientists to calculate the statistical probability of an unknown wood sample coming from a specific region, or population of trees.
But first, a database of intergenic DNA markers must be compiled from samples covering the species’ geographical range. This is exact what Lee’s team has done for cengal (Neobalanocarpus heimii), a valuable timber species which reportedly fetches up to RM10,000 per tonne, and ramin melawis (Gonystylus bancanus), a rare and endangered species which is trade-restricted and found only within dwindling lowland freshwater and peat swamp forests. Work is also currently under way to create databases for kempas (Koompassia mallaccensis) and dark red meranti (Shorea platyclados).
Being able to make geographical distinctions with regards to the place of origin of the timber has ground-breaking implications. It means that a DNA sample extracted from any piece of wood, be it a shipment going through customs or a piece of furniture, can be used to cross-check the source that is stated in the paperwork.
To take things a step further, stretches of DNA known as “microsatellites” are also variable, so these can act like individual fingerprints with only two samples from the same tree providing a perfect match.
Proving that misdeclared logs have not originated from a legal timber concession remains one of the timber world’s biggest challenges.
Section 15 of the National Forestry Act 1984 prohibits the taking of forest produce from permanent reserved forest or state land forest without a licence but it has yet to be the basis for any prosecution, partly due to the difficulties involved in producing evidence strong enough to stand up in court.
Lee says the primary application for his research is to furnish enforcement agencies with the necessary tools to do their job.
Microsatellite markers, for example, should be good enough to prove beyond doubt that there has been a chain-of-custody breach along the life cycle of a wood product, especially if the DNA can be matched to a specific tree stump.
Aside from helping with the prosecution of illegal loggers, there is a bigger picture his work is helping to build.
The data his team are generating can be used for fundamental sciences and furthering our understanding about the evolutionary genetics of tropical plants, and can also be used to identify biodiversity hubs and come up with more effective conservation strategies.
“Safeguarding our forests and figuring out how best to conserve them is important,” says Lee. “Because the forest doesn’t just belong to existing generations, but also to future generations.”
Due diligence through DNA