Deep within the rainforests of Borneo, a unique and increasingly rare fruit species, Mangifera casturi, makes its home. Known by local names including the Kalimantan mango, Kasturi, or Kastuba, this plant is a distinct relative of the common mango. It is a member of the Anacardiaceae family, the same family that includes cashews and pistachios. The fruit is particularly noteworthy for its intense and pleasant aroma, a characteristic that sets it apart from many other mango varieties.
Distinctive Botanical Features
The Mangifera casturi tree is a commanding presence in its native environment, capable of reaching heights of up to 25 meters. Its trunk, which can achieve a diameter between 40 and 110 centimeters, is covered in a smooth, greyish-white to light brown bark. The tree’s canopy is populated by elliptical leaves with pointed tips that are a striking dark purple when young before maturing to a deep green. Small, yellowish-green flowers grow in clusters known as panicles, eventually giving way to the tree’s fruit.
The fruit of the Mangifera casturi is considerably smaller than the more familiar Mangifera indica, weighing less than 80 grams. It has a distinct oval shape, and its thin skin is green, often speckled with dark or maroon dots. Inside, the pulp is a vibrant dark orange, with a fibrous texture and a highly aromatic quality that is its most celebrated feature.
Native Range and Ecological Niche
Mangifera casturi is endemic to the island of Borneo, specifically within the Indonesian region of Kalimantan. It has become a floral emblem for the province of South Kalimantan. The species originally thrived in the island’s lowland rainforests, found growing in areas with alluvial soil. These habitats are characterized by a moist tropical climate with significant rainfall and no prolonged dry season.
The plant prefers warm temperatures and high humidity. While it can be found in both dry and tidal swamp lands, it grows most successfully on dry land, particularly in sandy or gravelly soils that drain well. Although it was once a wild species, extensive habitat loss means it is now primarily found in cultivation within its native range, grown by private gardeners.
Culinary and Cultural Significance
In its native South Kalimantan, the Kasturi mango is a prized fruit, largely consumed for personal enjoyment rather than commercial sale. Its most common use is being eaten fresh, allowing its unique flavor and intense aroma to be fully appreciated. When in season, the fruit is highly sought after and sells out quickly in local markets.
Beyond being a food source, parts of the Mangifera casturi plant have applications in traditional medicine. The bark and leaves have been used in folk remedies. Scientific studies have indicated that extracts from the plant contain antioxidant and anti-inflammatory properties. The fruit itself has also been examined for its potential as an anti-inflammatory herbal medicine.
Conservation Concerns
The International Union for Conservation of Nature (IUCN) has classified Mangifera casturi as Extinct in the Wild. This designation, made in 1998, reflects that the species has vanished from its natural forest habitat and now survives only through cultivation. The primary driver of this disappearance is the widespread deforestation that has occurred across Kalimantan.
Massive clearing of land for coal mining and the establishment of palm oil plantations has decimated the ecosystems the mango once inhabited. The loss of these trees affects the wild bees, birds, and bats that relied on them. Conservation now depends on ex-situ methods, with its preservation happening in private gardens and conservation collections. Protecting the remaining genetic diversity of this species is important to prevent its complete extinction.