The Theory and the Reality of Shelterbelt Afforestation Projects

The Theory of Shelterbelts

The Reality

Introduction:  dust bowl, us efforts

Following the dust bowl years in the U.S. the government planted 220 million trees in a strip 100 miles wide, stretching 18,600 miles from Canada to the Brazos river.  1935-1942  Today, the growth and vigor of many trees has declined due to close spacing, age, and invasion of undesirable short-lived trees.  Wikipedia.

There are currently two major afforestation programs, one in China, and one in the Sahel.

Great Green Wall in China. 

This project aims to afforest 90 million hectares and eventually contain 100 billion trees in a 4500km belt.

A recent paper by Tan (2014) found decreased dust transport due to the plantings so far.  But independent Chinese media reported in 2013 that dust storms were increasing:  For centuries in northern China, annual sandstorms, called the Yellow Dragon, have been ripping through the city.  Wind erosion is obvious and most pronounced in spring, when sandstorms are common and the vegetation is still absent or dormant after severe winter temperatures. Sandstorms have increased in the last few years, calling into question whether the Great Green Wall is working.

Liu Tuo, head of the desertification control office in the state forestry administration, is of the opinion that there are huge gaps in the country's efforts to reclaim the land that has become desert. At present there are around 1.73 million sq kilometers that have become desert in China, of which 530,000 km2 are treatable. But at the present rate of treating 1,717 km2 per year, it would take 300 years to reclaim the land that has become desert.  

Background
In early times, Korqin was not a semi-desert, but savannah-type woodland, in transition between dense forest and the steppe zone. The rolling sand-sheet was deposited during the last glacial period (12000 years BP). During 10,000 years of vegetation growth, thick dark topsoil developed. Since historical times, the region has gone through several cycles of man-induced desertification and subsequent recovery, when human pressure lessened. Fertile dark topsoil vanished and extensive dune fields gradually build up.  Overgrazing (by cattle, goats, sheep, camels, horses), clearing of land for agriculture and over-cutting of trees and shrubs in this vulnerable ecosystem have resulted in an increasingly severe land degradation and desertification.

Other Approaches?

There are many who do not believe the Green Wall is an appropriate solution to China’s desertification problems. Gao Yuchuan, the Forest Bureau head of Jingbian County, Shanxi, stated that “planting for 10 years is not as good as enclosure for one year,” referring to the alternative non-invasive restoration technique that fences off (encloses) a degraded area for two years to allow the land to restore itself.  Soil fertility, already critically low, has shown a sharp decline as all organic residues from crops are removed for fuel and fodder during wintertime. Willow and poplar stands are pollarded in autumn, before leaf fall, for the same purpose. The continuous removal of potential nutrients to the soil is not balanced by the relatively small amounts of manure and inorganic fertiliser applied to crops.

Problems

 Jiang Gaoming, an ecologist from the Chinese Academy of Sciences and proponent of enclosure, says that “planting trees in arid and semi-arid land violates [ecological] principles”.The worry is that the fragile land cannot support such massive, forced growth. Tree growth in Korqin is largely dependent on the presence of a high groundwater table, fed by percolation and inflow from the western and southern mountainous areas. The long-term trend of a decreasing depth of the groundwater table is due to an increasing demand for water to irrigate crops and for human and industrial needs. If the trees succeed in taking root, they could soak up large amounts of groundwater, which would be extremely problematic for arid regions like northern China.  For example, in Minqin, an area in north-western China, studies showed that groundwater levels have dropped by 12–19 metres since the advent of the project.

Progress So Far

As of 2009 China’s planted forest covered more than 500,000 square kilometers (increasing tree cover from 12% to 18%) – the largest artificial forest in the world.However, of the 53,000 hectares planted that year, a quarter died. In 2008 winter storms destroyed 10% of the new forest stock, causing the World Bank to advise China to focus more on quality rather than quantity in its stock species.  FAO report

But the program’s widespread tree planting campaigns typically allot only one or two species of tree to an area. Professor Jiang wrote in a 2009 Epoch Times article, “In Ningxia, for example, 70 percent of the trees planted were poplar and willow. In 2000, one billion poplar trees were lost to a disease (Anoplophora), wiping out 20 years of planting efforts.”  FAO report followup

More criticisms:  Wikipedia.

Great Green Wall in Africa - the Sahel

The Great Green Wall initiative is much more nuanced than simply planting a belt of trees across the continent: “Behind the name or the brand ‘Great Green Wall,’ different people see different things. Some people saw just a stripe of trees from east to west, but that has never been our vision,” he says. “In Niger, Mali, and Burkina Faso . . . natural regeneration managed by farmers has yielded great results. We want to replicate and scale up these achievements across the region. It’s very possible to restore trees to a landscape and to restore agroforestry practices without planting any trees. This is also a sustainable way of regenerating agroforestry and parkland.”

But it should be noted that the Great Green Wall is not designed to prevent the Sahara Desert from expanding. “We are not fighting the desert,” he says. “In the majority of the areas we are working in these 11 countries, the desert is not advancing. The [Sahara] Desert is a very stable ecosystem. Of course, there are some areas on the margins—for instance in Senegal, Mauritania, and Nigeria—where there are some sand movements. But from a geographic perspective, over time the desert has been relatively stable in this area.” (Source)

But some authors advocate  "a shift from planting trees in the GGW to utilizing shrubs (e.g., Leptospermum scoparium, Boscia senegalensis, Grewia flava, Euclea undulata or Diospyros lycioides), which would have multiple benefits, including having a faster growth rate and proving the basis for silvo-pastoral livelihoods based on bee-keeping and honey production.” (Connors and Ford, 2014 Sustainability)

Problems with Roundup?

Roundup  was recently labelled by the WHO as a "probable human carcinogen".

But farmers still love it: LibertyLink soybeans testimonial

Because it works:  Time-lapse video of herbicide treatment


I previously wrote about chemical use versus abuse in American agriculture, as well as some of the new stacked-trait GMO crops that are resistant to multiple herbicides.

Geoengineering: Salmon Runs and Sequestering CO2??

A project to fertilize the oceans with iron to sequester CO2 and feed wild salmon runs has generated controversy.

Four Forests Restoration Project

The draft EIS for the first 500,000 acres has been released.

Thinning work is already ongoing, but is behind schedule:

"The company said it is now thinning about 30 acres a day, which works out to about 625 acres a month. That’s a significant increase in the pace of operations since January, but still far behind the schedule established for the project nearly four years ago.  Ultimately, the company’s 10-year contract with the Forest Service requires it to clear 40,000 acres annually. In the nearly two years the company has had the contract, it has cleared about 3,700 acres. That puts the company about 70,000 acres behind the original schedule."

In my experience, in the Jemez, the major time lags are for completing NEPA and EIS and waiting for good prescribed fire weather.  Cutting the trees is fast and easy, and if they skip the fire (unnecessary and possibly environmentally detrimental) nothing should slow them down.  One of my other main criticisms from the Jemez is that they're not thinning enough trees to reduce the basal area to the most beneficial levels.  I know the ideal density and pattern of trees has been argued about ad infinitum... it seems they are trying to avoid conflict by cutting less trees, which totally defeats the purpose of preventing catastrophic crown fire.

Fence Line Contrasts

Sitting on the fence has become a metaphor for ambivalence, but actual fence lines are some of the clearest lessons in land management.  Fencelines can be the best place to study ecology, because most fences divide two different land management histories.  The easiest places to learn from fence line contrasts is where the land management history is known.  For example, along highway right-of-ways (ROWs), the strip of land between the road and the fence is almost never grazed, whereas the private or public alotment on the other side of the fence has almost certainly been grazed and/or farmed.

However, just because the ROW hasn't been grazed doesn't mean that it has escaped disturbance. While comparing two disturbed areas can yield some insights, the multiple factors at work will make cause and effect deductions extremely difficult. To find a good comparison, look for areas that are relatively far from the road; immediately adjacent to the road is a zone of disturbance, which can include vehicle traffic, trash, mowing, and runoff from the road (i.e. increased moisture).

The best comparison areas occur where the ROW is relatively higher than road (so there is no possibility of runoff and little chance of other human disturbance).  However, areas with cutbanks below them are not good for comparisons, because of excess erosion, different microclimates around bare rock or exposed subsoil, and lowered water table.   A zone of depression in soil moisture can also occur around ditches, trenches, gullies, roadcuts, etc.

The actual fence-line itself may have different species due to fence-line drip of dew and the ability of fences to catch seeds, especially tumbleweeds. (photo).

On the ground immediately beyond the fence there may be an area of extra disturbance due to cattle trails, etc, and any areas near stock tanks or gates are also likely more heavily used (and hence a more extreme contrast).  In cases with less grazing on the private land, such as on steep hill slopes, vegetation and soils may look quite similar across fence-lines.  Of course, there will always be variable disturbance on both sides of the fence, but that is part of the challenge and opportunity of observing fence-line contrasts.

The best comparisons are between areas relatively far from disturbance, close to but not immediately adjacent to the fence-line.  With a good undisturbed ROW as a control, the vegetation on the other side of the fence can be compared to the potential climax community of the site.  

Case Example:

I was recently watching fence-lines along NM highway 285 from Vaughn to Clines Corners, and noticed that typical overgrazed areas are Grama Grass (Bouteloua gracilis) monocultures or low-stature annuals with large amounts of bare dirt.  The ungrazed roadsides still have bare ground, but the vegetation has a starkly different structure and composition:  multiple grass species occur with different growth forms.  But even more noticeable than the grass growth is the shrub encroachment in an area that is pure grassland.  Without fire or grazing, woody growth, especially saltbush (Atriplex canescens) and  Chimisa (Ericameria nauseosa) increases markedly.

While some trees and shrubs (e.g. E. nauseosa) are resistant to grazing when mature, their seedlings are highly palatable.  Cows can completely eliminate woody overstories from riparian areas in a single generation simply be eliminating recruitment (through both grazing and trampling) of Cottonwood and Willow seedlings.  Grazing pressure on seedlings is important, but easily overlooked: as long as there are trees, we describe an ecosystem as a forest. And it may seem strange to say that cows are eating a forest. But without seedling regeneration, no ecosystem is sustainable.

That grazing impacts woody growth as much or more than herbaceous growth is well-known along rivers and wetlands, but I think has been less remarked on in uplands.  From this brief study of fence-line contrasts, it appears that even more of our grasslands would support shrublands were it not for either grazing or fire limiting woody plant establishment.