It is now a safe prognosis that the climate gets warmer. Other components of climatic change and variations within Sweden are less certain predictions. Man adds a large contribution to natural changes, thus the future gets more uncertain than the past. How should the forest tree breeding system react to these circumstances? The reaction should not overshoot and risk thereby risk to make things worse, but moderate the effect of predicted change. Earlier it was to unpredictable what would happen locally and the change predicted was to small to bother, but now I suggest it is time to make a change The general reaction should be simple.
I suggest that we decide to now react as average temperature will raise 0.02 centigrade annually (a low estimate according to most Swedish scenario writers) from 1990 to 2100, and assume that change in whole Sweden is the same and that everything else is unchanged. The temperature before 1990 is assumed to be constant and quantitatively as it was 1961-1990 (reference temperature), thus by definition 1990 is here considered the starting year of rising temperature.
Transfer knowledge and performance of “natural provenances” and Tsum calculations is still mainly obtained from the reference period. Knowledge from later periods will have to be adjusted to the temperature rise, but that can wait. A change in temperature is considered equivalent with a change in altitude, the higher up the cooler. I suggest that the temperature is assumed to change 0.01 centigrade each m of altitude changes the temperature degrees, thus 100 m elevation rise decreases the temperature 1 centigrade. Thus the temperature climate 2090 will be as it was 1990 at start of temperature rise on a 200 m lower altitude.
I suggest Swedish forest geneticists respond to the global rise in temperature by making decisions and recommendations from now to sometime 2015-2020 as if it was 1990 but all elevations were 50 meter lower. That corresponds to the temperature around 2015. This is not optimal, but it is almost certain that it is better than no reaction to global warming, and it is a simple heuristic rule, while better and more sophisticated algorithms are developed. To accept a quantified change is a new thought, I suggest a more specific change is introduced 2020, when where is more experience with the first simple general change. Some cool bad years could happen during the next years and then the scheme would have convert back to 1990, but the chance seems small and the harm limited.
A question is how to act when elevation is below 50m. Negative elevations seem a doubtful concept and changing latitude for a small part of the area seem complex, thus the simpliest is to set altitude zero when it would fall behind. As the average altitude of the forest 0-50 m is 25, the difference in effect is halfed.
It can be argued that the temperature change has many effects. The average temperature changes, but the winter temperature will rise more than the summer temperature. The vegetation period will be longer. The climate can be said to be more maritime. The springs will come earlier and the autumns later. The spring and autumn months are warmer. The latest spring frost will occur earlier and the earliest autumn frost later. The exact prognoses are uncertain and I cannot find the information I would like to make exact prognoses. During the vegetation period the main change between temperature change by elevation and temperature change by global warming is probably that change by elevation has rather small effect in late autumn while global warming has rather large. It can be thought more over the details and someone ought to do that at some time. It can be argued that we should have a change in temperature sum instead, it can be regarded as similar, and the Swedish breeding population system is as targeted at temperature sums as at elevations, but a change with a constant temp sum means a larger change in elevation in northern Sweden than in southern Sweden. Or expressed otherwise, one degree of temperature change makes a larger effect of heat sum when the vegetation period is longer.
Trees in Sweden stand for almost a century and most of their growth may take place 50 years after their planting and having trees not adapted to the climate (e.g. as the growth cessation occur to early) may mean that they are not able to use the prolonged growing season. For foresters in cool Sweden the critical is how the trees thrive during the establishment phase. We do not want to risk recommending a seed source which is too mild. We have several instances of conceived too southern materials in Sweden (too southern pines (both Scots and lodgepole) on harsh sites in northern Sweden and Rumanian spruce in south Sweden), and we do not want to do such mistakes again.
The forest tree breeding system comprises three components: recommendation for foresters what to plant; recommendations for seed orchards establishers what material to use; and decisions for the long term breeding.
A seed source is recommended which is adapted to the climate of planting and some years after. Thus “planters guide” could “sink” elevation 50 m compared to the real when recommending material (and recalculate predicted temp sum for the locality). Thus forest regeneration material is “most” recommended compared to earlier recommendations as if the elevation of the plantation site was 50 m lower 1990. Foresters should still feel that they make their own decisions and have an own responsibility and what is the wisest choice may change locally, thus the change could, besides verbal explanation, just be that the default in “Planters guide” is to sink the elevation 50 m, foresters who think themselves may make own adjustments.
For seed orchard establishment it can be argued that the recommended use can be decided when the production comes. The “mistakes” introduced now by not considering global warming at establishment is that the projected areas for different intressents not will be optimal, and that forest tree breeders are likely to select material which is adapted to cooler climates forcing changes in recommended areas for the seed orchard to higher and more northern ones when the seed orchard was designed for. Seed orchards are long lived objects and (in contrast to plantations) the main crop will occur maybe 25 years after the selection of the clones. Thus it could be argued that a rise of 100 m would be justified instead. But it is simpler with a single rule and the first step is to consider the issue at all. A seed orchard comprises material from several breeding populations, typically targeted for areas close to the main target of the seed orchard. Today these neighbouring breeding populations get the same weight but now practically the seed orchard target can be modified for the future by choosing more selections from breeding populations heading for lower elevation that the target and fewer selections for breeding populations designed for areas above the target. Again 50 m is not firm but it is rather a recommendation to whoever appears as adviser to insist on at least that, if the seed orchard owner does not consider the issue.
For long term breeding decision the time span is also longer than establishment. Evaluation of the trial may be done 15 years after decision of what the site and the material choice. Again it is simpler with one thumb rule while more sophisticated are worked out, and that is to place the trials in the breeding populations at 50 meter higher elevation at and average that was foreseen when the breeding populations were constructed. It is possible to keep the geographic targets of the breeding populations, but I do not think that is the most efficient solution, because when some of the selection effort goes to change adaptation instead of being available to artificial selection. Also I think it is recommendable only to change elevation, not latitude, as if latitude changes it interacts with the light climate and the signals for growth cessation. Currently the breeding populations have wider variation than would be motivated from the land distribution just to be able to respond to the climate change which now happens so we can cash in some of the flexibility it gave to arrange breeding populations like this! However, to replace test plantations most coastal and at low elevations at a later stage I think it will be needed to move breeding material northwards. Here I suggest to let the breeding populations move only as much as the plantation populations, thus so it is right at the plantation of the test. It could be motivated to move them somewhat more as they are meant for the future, but when it is difficult to argue how much more. Breeding populations adapt to the change not forced on by moving them, the idea here is to reduce the needed adaptation, if we try to eliminate it, we can cause a reverse problem. Testing of breeding populations will also be done over a range, the most important is that future change is within that range when they are measured, the likelihood of that increases if we move the centre somewhat in elevation now.
There is some uncertainty about the influence on the spring frost problem of southern Sweden, but is seems spring frost incidents have been less common the last decade, might be that also is an effect of green house gases which may make a clear sky warmer, but more cloudy weather may reduce the spring frost risk. Warmer winters may lead to accumulation of a certain heat sum needed for bud development at a lower average temperature and thus raise spring frost risk. But the guess is that those effects will be very marginal and have little practical importance.
Trees are plastic and tree populations flexible. Tree populations can evolve and adapt. A hundred meter change in elevation is not a big problem and the change in heat sum is smaller than annual variations. 50 or even 100 m change for origin is marginal and makes not much, thus what I suggest is rather risk free, almost cosmetic if nothing big happens. However, global warming may have the same effect as a change of elevation 250 m some half century after planting and in a bad scenario and if local conditions interacts and that may make a considerable change. This change can be moderated to a considerable more benign effect if the change is reduced by 50 m by the change. Thus the change suggested is more for reducing the effect of a larger real change than that it matters if the real change is not larger than the suggested modification.
Do we overshoot with 50 m change in elevation? The temperature in the summer is predicted to change somewhat more than 1 centigrade per 100 m. The change is suggested to happen as fast as implementable but the effect is predicted first 2015. There are scenarios when the local rise will be smaller that the response. First 50 m is not drastic; the effect of an overshoot will be benign. Second we had some global warming already before 1990. Third, most scenarios predict a larger effect and when the consequences of not implementing the action will be worse. Third and half, the climate is expected to grow warmer after the plantation and trees not adapted to a warm climate may (e.g. by early growth cession in the autumn) may not be able to utilize the prolonged vegetation period, and thus loose much more in growth than predicted by missing 50 m in elevation. Fourth, by actually reacting we get a principle of reacting established, and once that is done the sophistication degree can be increased till next change, if we just discussed how probably a reaction will be too delayed. Fifth, for political reasons it is desirable that a reaction is made.
Seed orchard material can be assumed to be better suited to a changing unpredictable environment than stand seeds. First, it is tested material and test means test on many sites. Natural evolution knows only now and here, multi-site testing can be assumed to produce more stable material. Second, seed orchards comprise selections made over a region where the origin of the trees differ by hundreds of kms and selected based on different trials with a different history. Thus the seed orchard crop can be assumed to be more variable than stand seeds, where the parents often grow near each other. Under different conditions different trees can take over most of the production. Seed orchard crops have a buffering on the populations level. Seed orchards are rather predictable and reproducible and well defined, while stand seeds are likely to become more different and unpredictable in a situation with a drastic climatic change, where different stands will react differently.
Climatic change makes the future more unpredictable, thus it is an ambition to make each tree more plastic and more able to adapt to a variable range of environments than natural populations. Tree breeding in itself is expected to make trees more flexible as testing is made over a range of sites and decisions are made for the average. Still, as a response to an uncertain climatic change, the testing range of genetic materials could be somewhat wider than used historically.
An effect of breeding, seed orchards, intensified forests and climate change is that they constitute a strong incitement to decrease rotation age, and initially that means increase the harvesting. It is difficult to understand that so many factories close down in spite of that they are profitable, when for a layman like me it seems room for increasing the harvest instead. Anyway this is an aspect which does not seem sufficient discussed when the future role of the forest is discussed.