Tag Archives: forest harvesting

The Problem of Time in Ecology

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There is a problem in doing ecological studies that is too little discussed – what is the time frame of a good study? The normal response would be that the time frame varies with each study so that no guidelines can be provided. There is increasing recognition that more long-term studies are needed in ecology (e.g. Hughes et al. 2017) but the guidelines remain unclear.

The first issue is usually to specify a time frame, e.g. 5 years, 10 years. But this puts the cart before the horse, as the first step ought to be to define the hypothesis being investigated. In practice hypotheses in many ecological papers are poorly presented and there should not be one hypothesis but a series of alternative hypotheses. Given that, the question of time can be given with more insight. How many replicated time periods do you need to measure the ecological variables in the study? If your time scale unit is one year, 2 or 3 years is not enough to come to any except very tentative conclusions. We have instantly fallen into a central dilemma of ecology – studies are typically planned and financed on a 3–5-year time scale, the scale of university degrees.

Now we come up against the fact of climate change and the dilemma of trying to understand a changing system when almost all field work assumes an unchanging environment. Taken to some extreme we might argue that what happens in this decade tells us little about what will happen in the next decade. The way around this problem is to design experiments to test the variables that are changing ahead of time, e.g., what a 5⁰C temperature increase will do to the survival of your corals. To follow this approach, which is the classic experimental approach of science, we must assume we know the major variables affecting our population or community changes. At present we do not know the answer to this question, and we rely on correlations of a few variables as predictors of how large a change to expect.

There is no way out of this empirical box, which defines clearly how physics and chemistry differ from ecology and medicine. There are already many large-scale illustrations of this problem. Forest companies cut down old-growth timber on the assumption that they can get the forest back by replanting seedlings in the harvested area. But what species of tree seedlings should we replant if we are concerned that reforestation often operates on a 100–500-year time scale? And in most cases, there is no consideration of the total disruption of the ecosystem, and we ignore all the non-harvestable biodiversity. Much research is now available on reforestation and the ecological problems it produces. Hole-nesting birds can be threatened if old trees with holes are removed for forestry or agricultural clearing (Saunders et al. 2023). Replanting trees after fire in British Columbia did not increase carbon storage over 55 years of recovery when compared with unplanted sites (Clason et al. 2022). Consequently, in some forest ecosystems tree planting may not be useful if carbon storage is the desired goal.

At the least we should have more long-term monitoring of the survival of replanted forest tree seedlings so that the economics of planting could be evaluated. Short-term Australian studies in replanted agricultural fields showed over 4 years differences in survival of different plant species (Jellinek et al. 2020). For an on-the-ground point of view story about tree planting in British Columbia see:
https://thetyee.ca/Opinion/2023/11/02/Dont-Thank-Me-Being-Tree-Planter/. But we need longer-term studies on control and replanted sites to be more certain of effective restoration management. Gibson et al. (2022) highlighted the fact that citizen science over a 20-year study could make a major contribution to measuring the effectiveness of replanting. Money is always in short supply in field ecology and citizen science is one way of achieving goals without too much cost. 

Forest restoration is only one example of applied ecology in which long-term studies are too infrequent. The scale of restoration of temperate and boreal ecosystems is around 100 years, and this points to one of the main failures of long-term studies, that they are difficult to carry on after the retirement of the principal investigators who designed the studies.

The Park Grass Experiment begun in 1856 on 2.8 ha of grassland in England is the oldest ecological experiment in existence (Silvertown et al. 2006). As such it is worth a careful evaluation for the questions it asked and did not ask, for the scale of the experiment, and for the experimental design. It raises the question of generality for all long-term studies and cautions us about the utility and viability of many of the large-scale, long-term studies now in progress or planned for the future.

The message of this discussion is that we should plan for long-term studies for most of our critical ecological problems with clear hypotheses of how to conserve biodiversity and manage our agricultural landscapes and forests. We should move away from 2–3-year thesis projects on isolated issues and concentrate on team efforts that address critical long-term issues with specific hypotheses. Which says in a nutshell that we must develop a vision that goes beyond our past practices in scatter-shot, short-term ecology and at the same time avoid poorly designed long-term studies of the future.

Clason, A.J., Farnell, I. & Lilles, E.B. (2022) Carbon 5–60 Years After Fire: Planting Trees Does Not Compensate for Losses in Dead Wood Stores. Frontiers in Forests and Global Change, 5, 868024. doi: 10.3389/ffgc.2022.868024.

Gibson, M., Maron, M., Taws, N., Simmonds, J.S. & Walsh, J.C. (2022) Use of citizen science datasets to test effects of grazing exclusion and replanting on Australian woodland birds. Restoration Ecology, 30, e13610. doi: 10.1111/rec.13610.

Hughes, B.B.,et al. (2017) Long-term studies contribute disproportionately to ecology and policy. BioScience, 67, 271-281. doi.: 10.1093/biosci/biw185.

Jellinek, S., Harrison, P.A., Tuck, J. & Te, T. (2020) Replanting agricultural landscapes: how well do plants survive after habitat restoration? Restoration Ecology, 28, 1454-1463. doi: 10.1111/rec.13242.

Saunders, D.A., Dawson, R. & Mawson, P.R. (2023) Artificial nesting hollows for the conservation of Carnaby’s cockatoo Calyptorhynchus latirostris: definitely not a case of erect and forget. Pacific Conservation Biology, 29, 119-129. doi: 10.1071/PC21061.

Silvertown, J., Silvertown, J., Poulton, P. & Biss, P.M. (2006) The Park Grass Experiment 1856–2006: its contribution to ecology. Journal of Ecology, 94, 801-814. doi: 10.1111/j.1365-2745.2006.01145.x.

The Ancient Cedars Trail in British Columbia

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Whistler, British Columbia, is one of the famous ski hills in North America. Just north of the town of Whistler, above Green Lake, is a 4.5 km logging road that leads to the Ancient Cedars Trail, a 5 km round trip to see an old growth stand of several hectares of western red cedars (Thuja plicata). The red cedars are enormous, perhaps 700-1000 years old, and well worth seeing. But what disturbed me as I walked this trail is that this type of old growth forest with its rich diversity of tree species is what much of the forested world of coastal British Columbia and south-eastern Alaska used to look like, and I wonder what are we leaving in this part of the world for our great-grandchildren.

Trees are dollar bills in another form, and so the forestry industry thrives. But this is mostly crown land, not private land, and what do we the public get for this continual ravaging of the landscape? A strong economy to be sure, but is it sustainable? Forestry is sustainable if it allows ecosystem renewal at a time scale that is relevant to a human lifespan. Is modern forestry in British Columbia sustainable? We are told continually that it is.

Perhaps the paradigm is that we should log everything that can be converted into dollars, leaving a few hectares for the ancient cedars to remain. Then once we have logged up to the Arctic Ocean, we can come back south and start again. But will a logged forest ever recover as part of a forest ecosystem? And if it does will it take 300, 500, or 1000 years? If it takes that long, forestry is a mining operation, and from the point of view of our grandchildren the forests are destroyed not renewed.

The key issue for an ecologist is whether the forest ecosystem ever recovers after logging. It certainly does for some species but it is highly probable that other species are lost to the ecosystem. Part of this is because the forests that replace old growth are too often tree monocultures designed for optimum yield rather than for biodiversity maximization. So I think we should be more questioning when we are told an industry like forestry is operating sustainably. If it is sustainable, why are we logging old growth forests? If it is sustainable why are we logging 25° and 30° slopes? And what do we mean when we say that we are developing a forest harvesting plan when the time to recovery from logging is 200-300+ years? That is perhaps 3-4 generations of humans, more than we would like to tell our children. At a time when biodiversity conservation is being seen as more and more important, we are rushing ahead with logging old growth, hoping to get the dollars out before we find out that it was a mistake in management.

In the end we need to ask over and over again – what are we leaving for our grandchildren? And if you go walking in the coastal forests of western North America you need to look and then ask yourself what “sustainability” means, and whether the landscape is being managed sustainably. Perhaps many of our old growth forests in Canada are too important to be left to the management of the forest industry.