Saturday, May 13, 2017

The Sassafras: saving an endangered species

by Dexter B. Dombro

Preferred Sassafras habitat.

In the Orinoco River basin of Colombia there are several endangered tree species. One of them is the Sassafras or Ocotea cymbarum, a member of the Lauraceae family. It is listed in the IUCN’s Red List of vulnerable and endangered species. Its North American cousin was almost harvested to extinction, in order to make root beer, a beverage that was popular in the 19th and 20th centuries, and which is sold today as a type of soda pop, but thankfully without any Sassafras-based contents. 

Ecologists meet a Sassafras

The South American Sassafras has experienced similar uncontrolled extraction, primarily for its aromatic wood used in fine carpentry, but also in order to produce safrole oil for biofuel. In the 1960’s the use of safrole oil for human consumption was banned by the U.S. Food and Drug Administration, as studies suggested it is carcinogenic, with more bans that followed by European and other authorities. However, this did not stop the harvesting of Sassafras trees for carpentry uses.

Looking for Sassafras trees.

Ocotea cymbarum grows in the gallery forests and inundation forests of the Orinoco River basin. Its preferences make it a difficult species to work with. For starters, it prefers a lot of shade, which means that it cannot be cultivated in open settings. At the Reserva Natural La Pedregoza in Vichada, Colombia, planting experience shows that only those seedlings planted inside the rain forest survive, and that any attempts to establish the tree in non-shaded areas are a failure. This greatly limits the possible sites for restoration activities with this tree.

How to get up there?
Obtaining seeds from Sassafras trees is also a challenge. There are male and female trees, and only the  female trees have seeds. Due to past harvesting, this has caused further pressure on the species.  For example, when the natural reserve at La Pedregoza was established, only 4 mature Sassafras trees were found, 3 of which were males and 1 a female some 3 kilometers away from the males, making pollination extremely problematic. This low surviving density, more than anything else, encouraged the tree planters at La Pedregoza to make every effort to restore the tree to a self-propagating density inside the natural reserve.

Poor quality Sassafras seeds.
The seeds ripen in May and June, which coincides with the beginning of the wet season and the inundations. Since the trees have large, branchless and straight trunks and can grow to be over 25 meters in height, climbing the trees to collect the seeds is very dangerous. To add to the problem, the seeds are a favourite food for several types of fauna, especially macaws and parrots. This means that tree planters and birds are often in conflict when it is time to collect the seeds. Much relies on finding a compromise between the birds’ dinner plans and the needs of the tree planters when seed collecting time rolls around.

Good quality Sassafras seeds.
The seeds are quite large and very humid inside. This too causes a challenge, as only natural fiber cloth bags can be used to collect the seeds; otherwise they rot in the tropical heat. For that reason plastic bags are a complete no-no. For best germination results in the tree nursery, seeds should be no more than 1 week old from the time they are collected to the time that germination is attempted in the tree nursery. La Pedregoza has employed indigenous people to collect the seeds, a practice which has required considerable logistical support to get the seeds to the tree nursery in a timely manner.

Transporting Sassafras for planting.
There are only some 80 to 90 Ocotea cymbarum seeds in a kilogram (40 seeds per lbs.). Due to the many challenges already described the average cost of collecting a kilogram of Sassafras seeds works out to be about $100 USD, with no guarantee of germination. In addition, the manner in which the tree’s roots develop, means that larger planting bags are required in the tree nursery, each using a lot more substrate in order to fill each bag. The subsequent transport of the bags to a planting location is complicated due to the added weight caused by having large planting bags. Someone has to physically carry those bags into the rain forest, as vehicle access is not possible. 

Planting Sassafras in shaded spots.
 At La Pedregoza the average germination rate for Sassafras has been around 80% with good seeds. The  seedlings need about 4 months in the tree nursery, before they reach a viable size for transplanting in the forest. We use a 60% shading material while the seedlings are in the nursery, as they are quite sensitive to full sunlight even in their initial development. Since the seeds are collected quite late in the season, planting can´t really occur until October at the earliest, once flood waters start to recede from the inundation forest. La Pedregoza teams have planted Sassafras as late as December, when the final flood waters disappear.

Seeing if grasses will shade the tree.
Transplanting offers a further challenge, as any miscalculation in the selected planting site can result in a failure. Some natural predators seem to like to graze on the seedlings as well. In the past 3 years La Pedregoza has planted over 1,000 Sassafras trees in the rain forest, with only a 50% survival rate after one year. Working with Ocotea cymbarum is a labour of love, but considered by everyone to be well worth the effort, from seed collectors to tree nursery staff to the final tree planters, as well as the biologists and botanists supervising the process. The support of Tree-Nation members has been fundamental in this work, so everyone involved can truly state that they have helped save an endangered species.

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