What is Guano?
The word ‘guano’ derives from the Peruvian original language Quechua of “Huano”, which means “dung to fertilize”. The term Guano generally refers to deposits of excreta, carcasses and eggshells of seabirds, which transform under certain climatic conditions into the homonymous fertilizer. There are two main types of guano, the nitrogen and the phosphate guano. In Seychelles we have only phosphate guano.
Rock Guano
How is Guano formed?
As generations of seabirds consumed marine animals in the Indian Ocean, they often deposited the un-digested nutrients as excrement on the islands they used to nest and raise their young. Where significant quantities accumulated on islands with a calcareous subsoil (such as the many coralline islands of the Seychelles Archipelago), rain and sea surf caused the organic matter and phosphates from the excrement to leach into the bedrock. Whilst the organic matter will have decomposed, the phosphates did not and were left to react with the calcium carbonate in the subsoil to form ‘rock guano’.
Why was guano used as fertiliser?
What made guano remarkable was its high concentration of phosphates –one of the key nutrients, alongside nitrogen and potassium, needed for optimum plant growth. It also contains other chemical elements plants require for growth like sulfur, potassium, calcium, magnesium, chloride, boron, molybdenum iron, manganese, zinc and copper.
A Brief History of Guano
Despite the fact that the Peruvian had been using guano as a fertilizer for a long time, it never caught on in Europe until 1838. This happened when two Franco-Spanish merchants sent samples of the Peru guano to William Myers, a successful businessman from Liverpool, who was also interested in agriculture. The fertilization trials he has carried out with these samples must have been so successful that Myers invested in guano trading and ordered a larger quantity for the first time.
On July 23, 1839, 30 bags of Guano reached the port of Liverpool with the ship “Heroine”from Valparaiso. Myers distributed the guano to other interested farmers for experimental purposes. Crop yields skyrocketed and the bird fertilizer proved to be far superior to the hitherto common manure and the “Night Soil” harvested from the city latrines. At the instigation of importer William Myers, his local Peruvian business partner and companion, Don Francisco Quirós, in Lima, signed a treaty with the Peruvian state on November 10, 1840, for the monopoly on all guano mining. The demand for guano rose rapidly in England and shortly thereafter in the rest of Europe. The Guano boom began and individuals in Seychelles jumped on the bandwagon.
Cross-section of a block of guano. After being mined, guano blocks like these were crushed into a fine powder for use as a phosphate-rich fertiliser. Photograph by Theo Tomking, 2022.
The Guano workers
Since there was no permanent resident on most coral islands, labourers, mainly from Mahé, were transported to these islands with guano deposits to mine it from the bedrock. They would sign an employment contract locally known as lartik ( Fr. article d’emploie). This contract was very strict, and the worker could not return home until the end of the contract.
Working conditions were poor
Working conditions were poor and physically demanding, with loading of the guano onto schooners done by hand. Considering that 60 tons could be loaded in one day, it would have been exhausting work.
Correspondence from the then Governor of Seychelles in 1905, Sir Edward Walter Davidson, paints a picture of the working conditions. As Davidson writes: “on some islands I have suspected cases somewhat akin to ber-beri, probably due to the water – or the inhaling of the guano dust”. Considering that Davidson also recommended a doctor visit the islands, we can infer that work-related health issues were bad enough to warrant concern amongst even the elites of Seychelles’ political infrastructure. What we also now know is that Guano is one of the habitats of the fungus Histoplasma capsulatum, which can cause the disease histoplasmosis in humans. H. capsulatum grows best in the nitrogen-rich conditions present in guano. Furthermore, guano and its ammonia dust would have caused numerous health problems including eye irritation, and lung acid burns.
Seychellois Guano Workers Manually Extracting Guano
To add to the risks that such work involved, much of the guano deposits were on outer islands, so the transportation of guano back to Seychelles’ main port on Mahé could entail spending days at sea navigating dangerous currents. As Davidson writes in 1905: “The actual loading of guano is often accompanied by difficulty. … At all times there is a risk in navigation owing to the strength of the currents”. These records paint a picture of early guano extraction as a dangerous endeavour, built upon strenuous manual labour under poor working conditions.
The Profit Distribution
The guano mining was a very lucrative business and brought in great profits. As you might imagine, the fruits of this labour were not evenly distributed. These profits came at the expense of not just the workers, who had to deal with brutal working conditions, but also the ecology of the islands that were mined.
A significant portion of the profits from the guano industry went to those who owned or leased the islands with guano deposits. These were mostly individuals, but companies also ran mining operations in some circumstances. In 1906, for example, St Pierre Island was leased by the Crown to Captain G C Jouanis, whereas the entire Aladabra and Cosmoledo Groups, Astove and Assomption islands were leased by Mr. Adolphe d’Emmerez de Charmoy. Such individuals would have received the profits of the guano sold to exporters.
The other main portion of the profits went to the exporting companies, who ran the shipping operations that took guano from Mahé to other ports such as Mombasa, Port Louis, Liverpool and London and as far as New Zealand. The Seychelles Guano Company Ltd (later known as ‘The Seychelles Company Ltd’) was one of the largest exporters of Seychelles guano. In 1936, for example, they shipped just over 10,000 tons, supplying London, Liverpool, New Zealand and Mauritius.
The mining Process
The industry, relied on manual labor. The workers used picks, brooms, and shovels to loosen and then load the guano in gunny bags, ready for transport via schooners. The use of excavation machinery was impractical due to the terrain. Some islands like Denis and Assomption had a small rail system that carried the guano to a pier and on to a waiting ship. In other cases, the bags were loaded in pirogues and transferred to ships waiting at anchor.
Some export statistics on the Guano Industry in Seychelles
Guano exploitation on the outlying islands of Seychelles began in 1845, when guano from Coëtivy Island was sent to Mauritius to be used as fertilizers in sugarcane plantations. Guano exploitation was done mostly by private firms who were given leases of the islands in payment of a royalty to the Government and an export duty.
- Between 1895 and 1901, 12,774 tons of guano were exported for Rs 158, 644.
- Between 1901 and 1960, some 687, 453 tons of guano worth Rs 17 million were exported from the Seychelles.
- By 1963, around 700,000 tons of guano had been exported in total.
- Guano exploitation was still being done in 1964 when the export of 3,848 tons brought Rs 164,724.
Which Islands Produced Guano?
Most of the coral islands of Seychelles had guano but the ones that had guano in commercial quantity were: Denis Island, Bird Island, Rémire, St. Pierre, Platte Island, Astove, Assumption, Marie-Louise and Providence.
Some of the Main Islands of the Seychelles
I have tried to compile below a brief résumé of the guano mining output from some of these islands:
Denis Island
According to his log book, Jean-Francois Denis de Kereden, Count De Trobriand, mentioned that the island had good topsoil, presumably, he was referring to its guano contents. In 1903, W F Stephens visited the Island and later found out that half of the island was covered with guano. He estimated a total reserve of 25,000-30,000 tons. Large infrastructure with railway tracks and two jetties were built on the island to facilitate the efficient loading of visiting vessels, which took their cargo to New Zealand, Mauritius, and South Africa. The guano project was done to the detriment of the coconut industry. After they stopped the export of guano in the 1940, the whole island was rapidly replanted with coconuts palms.
I had the opportunity to spend one year on Denis Island as the resort manager and I was amazed to see how deep and wide some of the craters that were left behind are as a result of the guano mining.
Bird Island
It was reported by a passing ship in 1771 that the island was “covered with birds innumerable”. This was what created the high concentration of guano on the island. Guano mining operation was established on Bird Island in 1885. Between 1896 and 1906, 17,000 tons of guano were removed from the island and exported to the sugarcane fields of Mauritius. The mining operation supported nearly 100 people, the highest population of the island during her history. In 1906, the guano was exhausted, and most people returned to Mahé.
Rémire
Between the years 1950 and 1960, Rémire had a guano mining camp. The island was heavily exploited and excavated for its guano, with more than 100,000 tons extracted and exported. It even had a small tramway to transport the guano. The company involved was the Seychelles Guano Company. In 1960 the workers were evicted and the guano mine closed.
St. Pierre Island
In former times, much of the island was covered with a Pisonia grandis forest, in which large numbers of seabirds nested. The coral rock was thus covered with guano. The guano was mined away between 1906 and 1972. When the mining stopped the once densely forested island was left as a barren, pitted landscape. A description of the island from a 1968 soil survey paints a grim picture: “Only about twenty species of plants are present and, except for a few casuarina trees, the only surviving tree is a mapou (Pisonia grandis) in the centre of the island”. A more recent description of the island labelled it a “virtual ecological desert”.
Platte Island
Located 140 kilometres from Mahé, the main island, Platte Island, known for its low topography and proximity, has a history of guano excavation, which modified much of its natural biodiversity. In the 1840s there was sufficient guano on the island to make it worthwhile excavating. It is stated that by 1905 that 1500 tons had been taken off the island.
Astove
Guano extraction proved profitable and between 1927 and 1960 more than 72,000 tons of guano had been extracted but reserves were estimated at less than 5,000 tons. In 1968, the lease was passed to Mark and Wendy Veevers-Carter but later abandoned.
Assomption
Assomption Island is one of the most devastated islands of Seychelles due to guano mining, which destroyed the natural habitat. It was discovered by Captain Nicolas Morphey on 14 August 1756, and was named after the religious feast of the next day. In 1908, the island was leased to Mr H. Savy of Mahé, who built a coconut plantation there. The first settlement was in the northern part of the island.
Production moved from Coconuts to Guano
During a visit two years later, MR. Savy realized the guano potential of the island. The villagers transferred their labor force to a guano mining camp that operated from 1907 until 1983. Between 1926 and 1945 more than 160,000 tons of guano were mined and shipped out together with an unknown amount before 1926. Some deposits were recorded as being15 metres thick.
Part of the Guano Railway of Assomption- Note the Three Tracks and High Pile of Guano near the Shed
After 1945 the lease lapsed, and exploitation ceased in 1948; but with the renewal of the lease in 1955
mining began again. A mechanical crusher was brought to the island, and a small rail system was built to facilitate the transportation of the guano to the pier and then on to waiting schooners. In 1960 a survey estimated the reserves at 160,000 tons. Because of the sharp decline in the price of guano, production was at a standstill in 1967, and mounds of guano stood at the settlement unable to be shipped.
Remnents of the Small Rail System Dedicated to Guano Transportation
The loss of tree cover removed the nesting sites of what is now one of the rarest seabirds in the world: Abbott’s Booby (Papasula abbotti). Since 1909 reports claimed the species was extinct on Assomption. Today it is only known to nest on Christmas Island, on the other side of the Indian Ocean.
Abbott’s Booby (Papasula abbotti)
Marie-Louise Island
Marie-Louise was first sighted, and named, by Chevalier du Roslan in 1771. However, it remained uninhabited until the end of the nineteenth century. It was first leased in 1905, when the island had a population of 86 people. In 1905, two co-lessees ran the island, one overseeing the production of guano and the other developing agriculture. Over 3,500 tons of guano were exported from the island in late 1905. By 1906 it was reported that the economically workable deposits had been exhausted.
Below is a small extract in French from A. TONNET, (Magistrat Mauricien en mission) Traduit de son rapport de magistrat visitant les îles éloignées, 8 mai 1906.
« J’ai quitté l’île Alphonse le 24 avril 1906 à 18 heures et suis arrivé à Marie-Louise le 26 à midi… Marie-Louise est basse et sablonneuse avec un soubassement corallien. Elle est en partie recouverte de buissons et de petits cocotiers. L’île a deux concessionnaires : Monsieur Louis SOUCHON pour l’extraction du guano et le Capitaine JOUANIS pour la culture de l’île. Au cours de ma dernière visite à Marie-Louise le 21 octobre dernier, Monsieur SOUCHON a expédié 1 500 tonnes de guano à bord du Sydinham et le 26 du mois dernier j’ai trouvé quelque 1 200 tonnes sous le hangar prêtes à être expédiées. J’estime qu’il en reste environ 20 000 tonnes sur l’Île.”
In 1963, however, it was estimated that approximately 3,000 tons of guano remain on the island, of which half could be taken for local use without damaging agricultural potential. In recent times, it has been reported that guano for agricultural purposes has been imported from Desnoeufs Island. Following the exhaustion of guano supplies, the island’s main commodities turned to fishing and agriculture, supporting an island population of around 20 people. The island was neglected in 1969.
Domestic Consumption
Although most of the guano was exported, some was used for domestic purposes.
Crushed up and applied to the soil surrounding crops, guano made a potent fertiliser for the benefit of Seychelles’ agricultural industries. For example, on the coconut plantations that once sprawled across the plateaus of Mahé planters found in guano a seemingly inexhaustible resource to boost coconut yields and ultimately profits from their exportation as copra. Later, the Ministry of Agriculture also sold guano to local smallholder farmers. Some farmers would mix the guano (sold in fine powder form) with compost and apply the mixture to soils to improve plant growth.
The following interesting reports were extracted from a publication by B.H. Baker, intitled ‘Geology and Mineral Resources of the Seychelles Archipelago’:
P. R. Dupont (1907)
P. R. Dupont (1907), when curator of the Botanical Gardens at Port Victoria, in a report to Government described the guano deposits af St. Pierre Island when exploitation had only just begun and estimated the reserves at 200,000 tons.
For Astove, he estimated the guano reserves to be 6,000 tons, and for Assomption, 9,000 tons.
He also commented on the presence of small guano deposits on Picard and behind Cinq Cases on Aldabra atoll.
P. R. Dupont (1916)
A further report by Dupont (1916) dealt with Aldabra and its guano resources. In this report he concluded after seeing analyses of the Aldabra guano that it was not of sufficiently high grade for export owing to excessive leaching. He speculated on the origin of the iron and aluminium that occur in Aldabra phosphatic soils. He mentioned the possibilities that these elements may have been concentrated out of reef rock by leaching or have been introduced by floating pumice.
P. R. Dupont (1929)
Dupont’s most comprehensive report, in which he covered almost all the outer Seychelles islands, was written in 1929, when the outer islands were described as sand-cays or elevated reefs built on volcanic foundations. Each island was described, particularly from the agricultural point of view, and the formation of phosphatic sandstone beneath guano on the sand-cays was noted. Dupont reported that most of the high-grade guano of St. Pierre had already been exported. He also noted that about 5,000 tons remained to be extracted.
With reference to Assomption, he mentioned the difficulty of estimating its guano reserves even after five visits. But concluded that the original total amount of guano before exploitation was 100,000 tons of pit guano and 70,000 tons of surface guano of lower grade. He stated that in 1929 some 70,000 tons of pit guano remained.
The lesson learnt
It may not have been obvious then, but now we know that guano mining has undermined the ecological integrity of most of our coral islands. We have seen, as in the case of Assomption Island, how by removing the trees to extract guano, the nesting sites of what is now one of the rarest seabirds in the world: Abbott’s Booby (Papasula abbotti) was destroyed. Seabirds cannot defend their nesting ground but will abandon a site which is under threat and move to another. Some of our islands have lost entire bird colonies, like Denis Island.
Guano is also a vital resource in nature. It is now known that the nutrients that seabirds transport from marine environments and concentrate on islands through their poo, feeds plants and diverse invertebrate communities. The nutrients also trickle back into the ocean, helping tropical coral reefs to grow and recover from bleaching.
Sources
- IDC
- B.H. Baker, intitled ‘Geology and Mineral Resources of the Seychelles Archipelago’
- Sea, Soil and Extraction: The Guano Industry in Twentieth Century Seychelles, Theo Tomking
Any suggestions or comments about this post?
We welcome any suggestions or comments that will make this post more comprehensive. Please leave your comments below:
