Rainforest Day! (Written in combination with Erika DeBrouwer)
Today was rainforest day. The first question that we need to answer for you is why a rainforest is considered a rainforest. This is due to the elevation, the amount of rainfall as well as the temperature within the forest. A rainforest receives about 4 meters of rain per year, has a humidity of above 90% and has an average temperature around 26 but can be a high as 32 – 34 degrees Fahrenheit. La Selva currently has the longest standing data collection on a single area for climate. There is currently a rainy and less rainy season but lately there has been a change in the distribution of rainfall. This could eventually cause problems because the species within the forest need the humidity and if the rainfall distribution changes then the humidity will be affected. For the tour we split into two groups; Erika went with one guide Albert, and Christine went with the other guide Kenneth.
La Selva is a privately owned section of the rainforest that sits at an elevation between 50 and 3000 meters above sea level and when Central America emerged to connect North and South America and created the continental divide between the Caribbean and pacific sides of Costa Rica. The privately owned portion of the rainforest consists of 1500 hectares of lowlands and the rest is 64 kilometers of trails and 60 is paved. The entire rainforest is found on 50,000 hectares of both lowlands and highlands. There are over 300 species of trees, 1000 species of plants and 450 species of birds, in which over ½ of the entire bird population of Costa Rica can be found. Each guide took their group on a different route and saw different aspects of the rainforest. During our time walking in the rainforest each group saw a variety of different species. Christine’s group saw spider monkeys, white-faced monkeys, iguanas, peccaries as well as the Blue Jean frog. Erika’s group saw some different species including the howler monkeys, iguanas, peccaries, sloths, toucans, Blue Jean frog, the Bellbird, white bats, rupus morner, as well as many other species of birds. One interesting fact that John shared with Erika was that he added about eight new species to his list of species he had seen that day. Although we saw a lot of species most of the larger mammals are only found deep in the primary forest at more of a middle elevation.
The average age of the trees within La Selva’s portion of the rainforest is 200-250 years and range in height to about 50 meters. There are many different types of roots systems when looking at trees within a rainforest setting due to the lack of topsoil, nutrient retention and fast turnover rate. Roots therefore tend to spread horizontally instead of vertically within the soil profile. There are buttress roots, stilt roots, also known as the walking tree, strangling roots and aerial roots. Along the same lines as the different roots there are many epiphytes that can affect the trees. Most of the epiphytes are not hurting the tree and are only using it as support to get higher in the canopy and closer to the sunlight, but there are some that can be parasitic to trees. On a single tree you could have an unlimited number of epiphytes, however, if there is too many the epiphytes could be too much weight for the tree and the branch could break. Christine’s group spent all of their time in a primary forest which is over 100 years old; while Erika’s group spent some time in a secondary forest (30 – 35 years old) which develops into a primary forest, taking a minimum of 100 years if not more to complete the transformation. Competition within a primary forest is lower when compared to a secondary forest due to the lack of space. Trees falling as they age and competition between new trees competing and organisms occurs for the sunlight and the space.
La Selva is working with other organizations to aid in the development and protection of forested areas and to create a corridor through Central America for many different species. Currently there are pockets of protected forests throughout Central America, which is not ideal for migratory species, and the hope is to develop a complete corridor, not only for the migratory birds, but other animals as well. Not everyone in Costa Rica cares about conservation, an example of this is the pressure that La Selva feels when companies try to buy land for agricultural purposes. Even though La Selva is a privately owned rainforest, the researchers that work within the rainforest do not get paid for their work, rather they have to pay a yearly fee to be a part of La Selva and come to do research.
Many different species of birds exist within La Selva, and the few that Erika’s group had the privilege to see include: the Bellbird, the Lady Tailed Trogon, the Toucan, the Woodcreeper bird, and the Clay-coloured Robin, which were spotted within the secondary forest. This is because the mature forest is very dense and has a thick canopy, making it difficult for birds to cool down. Some interesting facts that Albert stated when spotting the Toucan and the Clay-coloured Robin, are that if you put a Toucan into a cage it would lose all of its coloring due to nutrient loss as their diets are highly diverse. The Clay-coloured Robin is the national bird of Costa Rica due to it’s beautiful song which is first song heard in the morning. Another point is that birds are not rehabilitated within La Selva due to its conservation practices and wanting to keep the forest as natural as possible. In order to introduce new species a permit is required.
There are 150 bats species that are important for the ecosystem as they are important for pollination and are a symbol of conservation. Within La Selva there are 75 species and they consume the seeds of fruit and then have the ability to spread the seeds to different areas of the forest. Bats are also important in aiding in the control of mosquito populations as they consume them as part of their diet, which allows aids slowing the spread of disease contracted from mosquitoes. The adult females of the bats are larger in order to carry the offspring during pregnancy and depending on the species it takes 8 months for the fetus to mature. The maximum age that a bat can reach is 40 – 50 years old and most of the species live at least 10 years.
Being a rainforest you would not think that soil erosion would be a problem. However since there is flooding all the time and the landscape of the forest is not all flat there is a lot of erosion. This was visible in the river as you could see the sediment that had been washed from the banks from an earlier rain. In 2005 it rained so much that the river was 2 meters below the bridge that we walked across. The water level was probably more like 7 or 8 meters below the bridge in February 2016. Every river in Costa Rica leads to another river leads to the border of Nicaragua and Costa Rica. This means that all of the sediment that is eroded is taken far from its origin. There is also potential that any chemical that are present in the water are washed away with the soil.
Our three learning points for the day were that biodiversity is key to the success of the rainforest as well as the interaction of the animals. The second was that soil erosion occurs in natural environments as well as managed environments and there are also very extremes on both ends in terms of the amount of erosion. The third learning point was that the change in elevation and the landscape, like a mountain, can effect many different aspects of the ecology within a rainforest such as vegetation, temperature and rainfall.
Although most of our day was packed with the excitement of La Selva, we did talk about the production of pineapples. John spoke about how pineapples are similar to bananas, as they are both highly monocropped, both use extreme amounts of pesticides, the uniformity of genetics is similar and major companies export, control and create contracts with farmers. That being said, pineapple is a very different crop production wise, they can be grown with slips (leave cuttings) or the producer can let the second crown grow. There is one pineapple per crop, but there can be two generations off of one plant. The preparation of land takes a month or over due to the importance of drainage. Ditches are crucial as pineapples aren’t tolerant to excessive rainfall. One interesting fact about pineapple production is that Costa Rica is the main exporter in the world!