Sunday, 10 January 2016

The life of an average tree

How long do you think trees live on average? You know that some trees can live for centuries - the Methuselah Bristlecone pine is over 4,800 years old, but even that age has been eclipsed. In 2010, the claim for the oldest living tree was more than 9,500 years for a tree that has a single root system that old but which periodically pushes up new trunks that only last a few hundred years. But if we count different tree trunks with a common root as a tree, then the oldest and possibly biggest living organism in the world must be the Pando quaking aspen of Utah, USA. The Pando is a single genetic individual, currently more like a forest with over 47,000 trunks, whose genetic makeup could be up to one million years old!

Wollemi Pine clones in the National Arboretum Canberra. How "old" are these?

And what about the Wollemi Pine, also known as the Dinasour tree? There are less that 100 trunks standing in the wild and it seems they are all clones having vegetatively reproduced somewhat like the Pando quaking aspen. Until recently we thought the Wollemi pine were extinct with pollen records disappearing after their hey days 121 million years ago. Are these remaining trunks still a single genetic individual from something started that long ago?

But on average? Probably the average life span of a tree is less than 2 or 3 years.

If some trees can live hundreds, thousands or even for millions of years how can the average be so short? Well, thousands, millions even tens of millions don't live more than a few months. They germinate and are eaten. Or they germinate but there isn't enough rain or sunlight or soil to keep them going and they die before the next rain. They can even germinate but then be poisoned by their parents via a process called auto-allelopathy to make sure they don't crowd the parents out. Even when the seedlings do survive and start to grow, there may be thousands of them per hectare with only room for, at most, a couple of hundred after a few decades. So, they compete for the space and most are supressed by those trees which eventually dominate the site. The supressed ones die during a stage called stem exclusion. So, a lot of trees die very young while very few make it to old age - making the average life span quite short.

But the story doesn't end there. While above ground the trees appear to be competing and even killing each other off, there may be a different story below ground. While exploring all the soil available to them, roots often come into contact with each other ...and often these roots fuse or graft themselves together. If enough roots graft together, sharing the photosynthates produced by the leaves above and the water and nutrients gathered below, how long is it before they cease to be separate individuals? Maybe all forests end up similar to the Pando Quaking Aspen, sharing a common root system even though there are hundreds of separate individual trunks with different genes above ground.

Does it even make sense to talk about the age of a tree in a forest anymore? It is like the human body and its cells. No cell in your body is more than 7 years old even if "you" are 50 years old. Trees, like cells, come and go but the organism can go on.

Happy New Year.

 

Wednesday, 2 December 2015

Species'ism

Is it ok to be species'ist - to advance one species or retard another just because of its species?

We seem to have concluded that racism and sexism - advancing or retarding individuals just because of their race or gender - is not ok. But what about whole species?

Species'ism seems to happen a lot in nature. In fact, a colleague and I recently found that one species of tree has been comprehensively retarded over 2,000 square kilometres of the Cooma-Monaro plains of southern NSW. Every individual Eucalyptus viminalis - Ribbon Gum - is either dead or dying in this extensive area. The Ribbon Gum was an iconic tree of this region, common on the rocky knolls and hills around fertile grazing and farming land. You can still see healthy trees in the region ...but if it is healthy it is not a Ribbon Gum.

We don't know why this one species is dying while the snow gums and other trees around are not. We do know insects are involved, but they are not the sole or even primary cause. We suspect that drought or changes to the rainfall patterns or to minimum and maximum temperature regimes might be affecting this one species to a much greater extent than others. There may even be some impact on this one species caused by changes in the local fire regime - too few, or too hot, or just too different to the pre-European fires. We do know that the once extensive stands of Ribbon Gum are all dead. We know this species won't be coming back at least for quite some time if ever. Nature, or the heavens, or even climate change has practiced species'ism to a fatal extent here.

We also know that something else will take over the place these trees previously occupied - something else will use the sun, the water and the nutrients that those Ribbon Gums used to use. Do we care what takes over? Do we want to promote one species over another? Should we actively intervene by planting our preferred species or be passive and just let any local "disturbance adapted" species win this 2,000 square kilometre home?

If a species that we do not want takes over this land, we define it as a "weed" and happily practice species'ism. But why should we choose not to want a species that can grow where Ribbon Gum clearly can no longer survive? The reasons for species'ism vary from the new species not providing the ecological services we are used to, through to aesthetics, and even that the new species are just "not from around here".

All trees provide a range of ecological services to different extents. They all produce oxygen, they all sequester carbon, they all slow and filter water. Some trees are more preferred as the habitat of birds or aerborial mammals while others are better at sheltering ground and bark dwelling insects. Some do more while some do less, but none will do exactly what a stand of Ribbon Gum used to do.

Aesthetics too are confusing. Humans tend to like what they are used to, and they have been used to Ribbon Gums in these lands. Although these trees have been dying for a decade now, so maybe the humans travelling through this region think dead trees are attractive!

Like racism, the argument that species are just "not from around here" is very often the only reason given for Species'ism. Often passionate arguments are made that only local species, grown from locally collected seeds should be planted in any restoration or revegetation project. But, the local Ribbon Gum will no longer survive. So, do we plant Ribbon Gum from areas far away that might cope with whatever killed the current trees - the natural range for Ribbon Gum is extensive and goes from Tasmania through Victoria and up the coast of NSW and someone could probably trial a huge selection if there was time. Does that violate the "not from around here" bias? But if we don't really know what killed the current Ribbon Gum, how could we really risk planting more Ribbon Gums? Is a Ribbon Gum grown from a seed collected in Tasmania more "local" than seed from another species of Eucalyptus grown only 10's or 100's of kilometres away from the dead Monaro plains? How important is it that the species remains "pure"?

How do we value the trees and their ecosystems services and aesthetics? How do we balance our understanding of the history or iconic nature of one species with the risk its time has come! How do we choose between species? These are not simple questions and they can't be answered by by scientists or economists or conservationists or engineers or community activists or even artists working alone.

 

Wednesday, 9 September 2015

Three Trillion Trees

A new report out of Yale University and published in Nature concludes that, globally, there are over 3 trillion trees alive today! This figure, they say, is substantially greater than the previous estimates of only 400 billion trees. However, the study also concludes that the world is loosing 15 million of these trees every year. Some really big numbers there, and given that measuring forests is actually one of my areas of research, I have had my 5 minutes of "fame" on national radio and TV talking about these numbers.

Is the beauty or the value of this scene related to the number of trees?

"How did previous researchers get it so wrong?" is the question I get asked, often with the follow up of "does this new information change anything?" Well, I am not entirely positive that the new estimate of 3 trillion trees is totally right either, but don't think details about non-normal error distributions and back-transformations would make anybody other than statisticians, biometricians or mensurationists sit up and listen - so I. Won't talk about that here. But if the differences between the estimates are real, it is probably more likely to be due to previous studies not being interested in the number of trees - they simply estimated that for completeness. "But why wouldn't we be interested in the number of trees?" I sense you asking. The number of trees is only useful when you know the size and distribution of those trees, so most previous studies have concentrated on estimating total biomass, carbon or volume of the trees and mapping that. These total values essentially are the result of multiplying number and average size together and so totals give you both in the one figure. A forest with 10,000 small trees may have the same biomass as another with only 800 large trees, so loosing 800 trees may be important in one forest but not in another. However, a forest with a large biomass will tend to have greater biodiversity, stored (sequestered) carbon and other ecosystem services than a forest with low biomass. Studies of isolated trees in farm paddocks and urban areas demonstrate that even a single tree of the right size and in the right place may have substantially greater value to ecosystem services, birds, animals and even aesthetics than hundreds of trees elsewhere. With trees, it is not always the case that not plus one equals two!

The number of trees also changes substantially in any patch of forest over time. In eucalyptus forests after a major fire, thousands or even tens of thousands of trees may germinate and race towards the heavens. However, as early as three years of age, these trees will start to compete and many will die so by about 80 years, there may only be about 500 - 800 trees left living. Then however, other types of trees (shade tolerant ones) might get involved and start growing underneath these surviving eucalyptus giants, so the number of trees start increasing again. Given enough time, those original eucalypts will die of old age or wind and fire damage (number goes down again) which might allow a whole new race of young trees for the heavens (increasing the number). While the number of trees goes up and down through this natural sequence, the total biomass and even the total biodiversity tends to always increase. So, it is better to measure biomass than number of trees because it is more closely related to what we really want to know about, and it is also easier because we don't have to worry about the noisy increases and deceases in number through time.

So, was there any advantage in undertaking and publishing this study on the number of trees? It may be simply that people have a better understanding for numbers of a count of trees rather than the area in hectares of forest or the biomass in tonnes. People might be able to connect better with the idea of 15 million trees being lost each year to agriculture whereas they cannot come to terms with thousands of hectares undergoing land use change. People in general are not too good at estimating area once it gets beyond, say, a football field (do you know how big a football field is?). We may be even worse when estimating weights - how many tonnes is a Blue Whale, so how many equivalent Blue Whales are cleared for agriculture this year? On the other hand, do you really appreciate how many zeros there are in a Trillion?

The Nature article itself stated that civil societies resonate with programs like the "Billion Tree" or even "Million Tree" urban planting goals, so putting a count of the number of trees might help civil society to comprehend the size and importance of the forest. This is probably the greatest benefit of the study - and certainly the reason I was invited to the TV and Radio for my bit of fame. Fame and civic awareness of forests are certainly good things even if forest ecologists, scientists and foresters wont really care about the final big number.

Me at the Canberra studio, waiting for the Prime Minister of Australia to finish so I can have my say on trees.

 

 

Sunday, 21 June 2015

800 year celebration

This year, many are celebrating the 800'th year anniversary of the Magna Carta. While many claim this is the start of modern Law (at least, the British sort), it was a 'win' for the Barons over the King: the King was now answerable to the Law and the Barons, and not 'just' to God at The Day of Final Judgement. Actually a lot of merchants won too - it was their assistance that resulted in the Barons getting the upper hand, so they were rewarded.
But the document that was signed (or for the pedant, sealed) 800 years ago offered a lot for the struggling peasant too. So much in fact, that many of these benefits for the peasants were separated from the "Great Charter" into a companion document called the "Charter of the Forest". The forests were vital for the peasants - they used its resources for energy (fire wood); grazing; fodder; collecting food like berries and mushrooms; and building. Access to the forest could even be thought of as a medieval version of the dole - if you had no home and no family support, you could meet the minimum of your needs from the forest. But the Kings had been progressively alienating the peasants from their forests and claiming more and more to the sole use of the sovereign. Robin Hood was famous for killing the foresters who were enforcing the King's rules as much as for his giving stollen goods to the poor! The Charter of the Forests returned to the users of the forest their rights of agistment, estover, pannage and turbury (or rights to graze sheep, pasture pigs, collect firewood and cut turf). A recent study showed that peasant and small family groups can continue to exercise these right for generations without destroying the forest.
Collecting sticks in a public forest. Firewood, shelters or just a game?

So, how are things today 800 years after the The Great and The Forest Charters were sealed? Well, the Law is firmly established with respected and noble traditions. The Barons have changed from being owners of vast tracks of land to being owners of vast mineral reserves and coal deposits, or chains of factories, newspaper and entertainment services, while the merchant class still funds the changes in the modern world. But the peasants or the free men and women (in our modern parlance - the taxpayers and the struggling mums and dads) do not appear to have been able to take up their benefits from forests. In some states of Australia, over 50% of the forests are reserved for the sovereign (government) and the peasants may only look, or if they are young and fit, walk but not touch. Modern-day Barons may take timber or graze industrial scale flocks of cattle or even mine in the rest of the forest, but individual peasants can't remove or use anything to meet their personal or family needs. In fact, there is increasing pressure to keep peasants and people of all sorts away from the forests altogether - keep them corralled in articifial castles cut off from the outside world.
Has the Charter of the Forest ever been repealed? Is it too late to exercise the right to take the forests back from the Barons and the Government? The peasants and free men and woman of the modern world cannot live in the forests full time any more, but they can reconnect to their heritage and their nature if they occasionally exercise their right to collect a bit of fire wood for themselves and maybe BBQ a meal or two. We should certainly have as much right to that as we do to receiving the dole. Might be cheaper and healthier for everyone too.
So, this year, celebrate the Magna Carta with a walk through your forest.
A medieval forest, from Livre de chasse (1387) by Gaston III, Count of Foix.



Wednesday, 27 May 2015

Reserving a big new National Park

If the current reserve system in Victoria - both formal and informal - cannot save Leadbeater's Possum, why would just adding area to the formal reserve system will make a positive difference?

A substantial increase in the formal area of reserve in Victoria, by itself, would not "save" the possum. At the very least, such an increase would need to occur in conjunction with an even more substantial increase in funding and resources to offer a chance of success. It is myth that National Parks can simply be locked up and left to follow healthy and sustainable trends. In cases where reserves have been simply fenced in, the ecosystems often drift off to something unexpected and undesirable as the result of altered fire or flood regimes, or invasive species, or a combination of factors. Active management, resource intensive management, will be increasingly needed for our existing reserves to "save" species in the face of ecological change wrought by climate change and other human impacts. Extension of the reserve boundaries will have to consider active management and substantial increases in funding. No doubt this will be an uncomfortable debate for many people, but one that is needed.

These extra resources won't be just for an extension of the track system, or better maintenance of fire trails, or better rubbish removal, or even more research that describes the current populations. In the specific case of Leadbetter's possum, if the lack of habitat hollows is already a population threatening problem, and hollows are not being formed naturally at a sufficiently fast rate, then active management will be necessary to correct this imbalance - just waiting another 70 years and hoping everything survives that long is not a recipe for success. The predominant factor relating to hollow development is tree size, and Foresters especially trained in silviculture and forest ecology, know how to manipulate population pressures within a forest to ensure a minimum number of trees can grow to reach the size to support hollow development in the minimum amount of time. Further, they can appropriately "damage" the crown of appropriate trees to speed up hollow development. The wait for hollows to home the possum can be substantially reduced from 70 years with active management. But such an exercise is expensive, labour intensive and will require some trees to be felled.

An even greater problem for under-resourced reserves is that weeds will take natural advantage of increased stress caused by changes in fire regimes or climate. Similarly, pest populations will boom as natural control mechanisms falter under already observed changes. How will the existing reserve system cope if Australia suffers a pest outbreak like the mountain pine beetle experienced in Canada? What happens to the potential for control or mitigation if the reserve system is twice as large due to an under funded increase in area? Active management was seen as an essential part of coping with this pine beetle outbreak with the Canadian Government providing substantial funding to First Nations, communities and school districts for fuel management and hazard tree removal in post-infested areas, as well as recovering some costs by selling the killed timber.

Changed fire regimes in the US have changed the species composition and structure of the forests leading to more mega fires than ever before. Active management is being pursued in the U.S., and products are being sold to offset some of the costs of management. United States taxpayers are fully funding their program but American Professor Scott Stephens said about 40 per cent of the cost of implementing the program is covered by repurposing the cleared timber (i.e. selling it as garden mulch, woodchip, fence posts of even sawn lumber).

An increasing concern is that Eucalypts have particularly poor dispersal capabilities, so natural stands will be generally be unable to track changing climatic conditions. (Booth et al, 2015). Will active management be needed to translocate species to new environments? Species like the "pioneer" Eucalyptus that dominate after a fire, need bare ground at least 80 m from standing dominant trees for their seeds to germinate and grow well. However, if the climate warms and the rainfall patterns change as predicted in many reputable Australian climate models, will these large gaps of bare earth may become too hot and dry for successful natural regeneration? Will reserve workers need to manually plant and water seedlings to avoid a species change?

More money and resources need to be allocated to the existing Reserves and National Parks to give a chance to "save" what humans hold precious. Substantially more funding will be required if the area of reserves increases - there is little opportunity for "economies of scale" in the reserve system management because each additional hectare added is unique. Without a substantial increase in general tax payer funding the reserve managers need opportunities to co-fund their own maintenance and safe keeping. Payments for ecosystem services have long been held out as a way of generating these sorts of funds, but the mechanisms for such funding are far from developed and active. Sale of products extracted from the reserves, especially when the mass of those products may themselves be contributing to the problem, is a much more immediate source for funding.

 

Monday, 20 April 2015

Planting Trees: a thing that sets us apart.

Many attempts have been made to uniquely distinguish humans from the other animals. Use of tools was a promising one until we observed birds and monkeys using stones and sticks as basic tools for getting into shells and ants' nests. Speech also showed promise until monkeys learnt significant vocabularies in sign language. Farming - but no, ants farm fungus in their nests. Even burying our dead is no longer seen as a uniquely human trait. So, what action makes humans significantly different?

I suggest the fundamental difference is a human tendency to plant trees. Yes, planting trees - but not just as a crop or for the fruit and wood they might produce. All animals need to do things to provide food and shelter. Humans can and do grow things to harvest for food and shelter. But planting a tree is much more.



Squirrels harvest nuts and hide them and ants collect seeds and store them in larders. If these nuts and seeds are forgotten or otherwise left alone long enough in the dark and damp they may germinate but this isn't really planting a tree. Birds and insects are vitally important in the whole fertilisation business, but that isn't planting a tree.

When a human plants a tree, it cannot help but be a symbolic gesture. You must be aware of the scale of time and that you are making a gesture towards a promised future. It is a gesture of hope. You must be aware that the planting is to benefit those who come after you: your family; your children or grandchildren; your neighbours; the other animals of your environment. Humans have the ability to foresee and plan for their future even beyond their own death. We have a need for acts of faith, acts of renewal, ritual confirmations of continuity that is met uniquely in tree planting.

Even planting fruit trees is so much more of a symbolic act than farming annual crops like wheat or rice. You may fully intend to consume the produce from that tree, but not until some point in the future. A future at least years away, that you have imagined, that you have hoped for and believe you can bring about. A future of peace and justice enough for you and your children to enjoy the fruits of your labour. A future that may include quiet contemplation while sitting under the shade and in the comfort of the developing crown. A future in harmony with nature and bees doing their 'thing'. A future that may even include tree houses or at least the excitement and drama of tree climbing. A future that you are actively bringing into existence.

How right and proper it is that trees are planted in our civic places to symbolise remembrance, or nationhood, or bonds between cities and nations, or peace. Trees are an analog for peace and for most humans the planting of a tree is one of the most hopeful things anyone can do.

But every planting of a tree symbolises these things. It is the planting of such symbols that sets us apart.

If you have not planted a tree and looked into the future then you don't know what it is to be truly human.



Friday, 13 March 2015

Forestry in an Egg Shell

Eggs occasionally receive a bad rap. "Cholesterol death bombs" was one headline in the 1970's, and eggs are commonly identified as the source of salmonella poisoning scares even now. However, with the exception of badly prepared meals, eggs are seen as a healthy and sound food source, and certainly of superior value to artificial alternatives. Up until the late 1960's it was not uncommon for suburban households, even in a metropolis like Sydney, to run a few chickens around their backyard - great for dealing with table scraps, providing a regular source of wholesome breakfasts, and serving as the main course in the occasional celebratory dinner. Purchasing eggs in the shops during this time was relatively expensive, and getting a chicken to roast from the butchers was a Christmas or birthday treat. But in the 1970's, the "economies of scale"  were introduced to chicken and egg production. Suddenly, battery farms could produce eggs for market that were cheaper than raising them yourself and chicken -roasted or deep fried - became the mainstay of cheap "fast" food. Backyard coupes, no longer needed, disappeared as houses covered more of the block and our population feasted on cheap chicken and eggs.

I believe plantations are battery forests, the equivalent to the battery farm goal that focuses attention on cheap and intensive production of a good.



It has taken a couple of decades, but the true costs of the transfer to battery farming have come home to roost (sorry - just had to use that pun!). Financial costs, health costs, social costs and moral costs. Battery farming is intensive and uses disproportional quantities of energy, water and nutrients compared to the traditional backyard coop. To control diseases in the crowded conditions, battery producers include "preventative" antibiotics, while mega-doses of vitamins make those saleable orange yolks. No doubt, battery produced eggs are still better for human consumption than many alternative foods, but despite the chemical and drug additions the battery eggs tend to be worse for health than backyard eggs. For example, battery eggs have higher levels of "bad" cholesterol levels compared to those produced by chickens free to forage for insects and grubs on the open ground. Chickens also taught generations of children about life, nurture and death - they were probably the original "birds" in the stories about the birds and the bees! Children learn even as they enjoy being around free range chickens.

The "costs" of the pain and suffering of the caged chickens has more recently come into the equation. More consumers are moving away from cheap battery eggs to demand "free range" and less morally stained eggs produced from chickens free to roam over hectares of land.

So, how does this relate to the forest? Centuries ago, forests were essentially the "back yards" of the human populations. With no intensive management, humans took their daily needs of fuelwood, building material and even foods from the extent of the forest. Children and their parents were linked into the natural world of life and death; birth or regeneration; and the complex interaction of the living things. The forest users were the forest dwellers and they saw how the forest grew, how it responded to damage, how it produced goods and services that could be treasured and safely used. Fast forward to the late 1900's when "battery forests" or industrial plantations were touted to replace the extensively managed "free range" forests. The children moved out of their backyards even as wood became cheap. Are we suffering the same sort of losses as experienced with the loss of the backyard chicken coop?

Like battery farms, battery forests use a disproportionate amount of water, nutrients and energy compared to the older "backyard" or extensively managed alternatives. Plantations have to grow fast to be a commercial success, and that means adding fertiliser and water. Now, legislation and regulations are in place in many states to limit where battery forests can be established and so minimise their use of ground water.

Our urban populations do not interact with these new forests and are increasingly isolated from the old forests so they no longer know how quickly a tree can grow or the conditions trees need to set seed and successfully regenerate. They no longer know which animals use what habitats provided by the trees, or even that these very habits change over time, growing and decaying with the tree. When backyards ceased to house chickens and compost heaps and places for children to learn and grow, these places were re-tasked, built over, or left to grow weeds and "store" junk. Will our forest lands suffer the same as children no longer walk through them or use them? Already the Australian Government's much vaunted "Green Army" is often reduced to cleaning up weeds and litter in the backyard forests that urban populations no longer care about or venture into.

But, don't get confused. The products from these plantations are still vastly superior to artificial alternatives just as any egg is better than junk or snack food. Wood as a building material, even from plantations, consumes far less energy to produce than plastic, steel or brick even while it stores carbon in a long-term pool. Paper produced from a plantation similarly is the result of less energy and pollution than paper produced from agricultural residues or non-biotic (and exhaustible) alternatives. Even fuel produced by plantations (fuelwood, biofuel) causes less damage than non-biotic sources, or sources that release the CO2 that was removed from the earth's carbon cycle millennia ago.

Unlike chickens, trees don't obviously look stressed when forced to grow in battery situations. But trees do suffer stress - growth stress. Eucalytpt trees in particular exhibit stress when grown quickly. This stress is 'released' once they are sawn into structural timber. But the release can be explosive with the boards twisting and bending, and ending up useless as a building material. In contrast, trees grown in the extensive backyard forests produce stronger and more attractive structural materials.



The cost of egg and chicken production has changed dramatically over time. The value of the product has also changed even while the production process cycled from extensive to intensive and back. But there will always now be a mix of the free range backyard and the battery chicken. Will the value of forest products and the process similarly change as management cycles from extensive to intensive plantations, and maybe back again? What is balance between extensively managed forests and battery forests, and how do we get there?