The Congo Rainforest Without Elephants: An Uncertain Future
By Emma Silva
It is no small secret that the African forest elephant population is declining. Poaching and deforestation pose a major threat to the extinction of these gentle giants. In the last decade, over 60% of the forest elephant population was killed because of poaching, and the remaining population roams less than 25% of their historic range.¹¹ The potential extinction of African forest elephants is a scary enough prospect for conservationists to rally people against poaching. However, the extinction of African forest elephants could also change the Congo Rainforest as we know it.
African forest elephants are considered “keystone species” in African rainforests, meaning that their impact to a particular ecosystem is greater relative to their biomass.¹ ⁶ They play a critical role in maintaining the structure and function of Afrotropical forests. Researcher John Poulson and his colleagues hypothesize that the decline of African forest elephant populations will drastically change the composition of Afrotropical forests.⁹
Elephants are the largest fruit-eating animals on the planet and may consume a greater variety of plant species than any other animal in the world.³ Elephants are monogastric gut fermenters, so breaking down defensive plant toxins common in tropical forest plants proves difficult for these creatures. Consequently, elephants increase their food diversity to prevent ingesting too much of any specific toxin.³
Forest elephants play a key role in seed dispersal within Central African forests. Elephants travel much farther distances before depositing seeds in comparison to any other dispersing agent.¹⁰ One study tracked 4 GPS-collared elephants through the Congo Rainforest, focusing on the distance of seed dispersal from ingestion to defecation. 88% of the seeds were dispersed over 1 kilometer away from where the seed originated, and some seeds travelled as far as 53 km before being dispersed.¹
In addition, many seeds benefit from being ingested and defecated by elephants. Elephants tend to disperse large seeds and fruits characterized by fibrous pulps and hard seed coverings, plants that would otherwise find difficulty dispersing on their own.⁶ As a result of high predation, some plants develop hard seed coatings to protect themselves. Unfortunately, it also makes it difficult for the seeds to germinate.³ However, when broken down by digestive enzymes of the elephants’ guts, the seed may be able to germinate.³ In general, studies show that most seeds that pass through elephants’ digestive tracts show a reduced germination time, better growing rates, and greater seedling survival because of the nutrient-rich environment provided by elephant dung⁸ and the digestion of the seed coating.
For some plants, such as the Balanites wilsoniana, elephant dispersal is essential for survival.⁴ Elephants are this canopy tree’s only effective dispersal, and germination increases by around 4000% when ingested by an elephant. Without the elephants’ role in dispersal, plants like the Balanites wilsoniana would cease to exist.
In addition to seed dispersal, forest elephants play a critical role in nutrient recycling. Because of their high dietary diversity, elephants cycle a large variety of nutrients within the forest ecosystem, providing plants with the nutrients needed to survive.² African Forest elephants also excavate termite mounds and salt licks, distributing minerals that may have previously been unavailable.⁷