The forests of Goa are typical of the Western Ghats (Southern Maharashtra and Karnataka). However, there is diversity in these forests due to variations in altitude, soil character, slope etc. According to the Champion and Seth (1968) Classification of forest types of India, the forests of Goa can be categorized into the following types:
(i) Estuarine vegetation, consisting of mangrove species, and found on narrow muddy banks of rivers
(ii) Strand vegetation along coastal belts
(iii) Plateau vegetation confined especially to low altitudes
a. Open scrub jungle
b. Moist mixed deciduous forests
c. Secondary moist mixed deciduous forests
d. Sub-tropical hill forests
(iv) Semi-evergreen and evergreen forests
a. Semi-evergreen forests
b. Lateritic semi-evergreen forests
c. Evergreen forests
Most forests in the state are located in the interior eastern regions. The Western Ghats, which form most of eastern Goa, have been internationally recognised as one of the biodiversity hotspots of the world. The February 1999 issue of National Geographic Magazine compares Goa with the Amazon and Congo basins owing to its rich tropical biodiversity.
I) ESTUARINE VEGETATION OF MANGROVES ALONG SWAMPY RIVER BANKS
This occurs in small, isolated patches along the banks of the Mandovi and Zuari rivers and other salt water streams. Botanically, this zone is characterized by peculiar root formations (stilt roots of Rhizophora, pneumatophores in Avicennia, knee root in Bruguiera etc). The mangroves are found mainly at Durbhat, Panjim, Agassaim and Cortalim.
II) STRAND & CREEK VEGETATION ALONG THE COASTAL BELT
Most of the coastal regions of Goa are rocky, with projecting ridges. The strand vegetation is limited to a few patches of narrow strips bordering the Arabian Sea. The vegetation along the south bank of the River Mandovi, near Panjim, belongs to this category. The main tree species are Pongamia pinnata, Thespesia populinea, Calophyllum inophyllum, Cerbera manghas and Pandanus tectorius. Herbaceous species such as Neanotis rheedei, lphigenia indica, Begonia crenata, Habenaria grandifloriformis, Tricholepis glaberrima, Trichidesma sp. are found along the rocky creeks and projecting ridges facing the coast.
III) PLATEAU VEGETATION ALONG UNDULATING TERRAIN & HILLS
A major portion of the vegetation in Goa belongs to this category, which is further divided into four types ie (a) Open Scrub Jungle, (B) Moist Deciduous Forests, (C) Secondary Moist Mixed Deciduous Forests and (d) Sub-Tropical Hill Forest.
(a) Open Scrub Jungle: This type of vegetation occurs from Panjim to Cortalim, and from Bicholim to Sanquelim. Anacardium occidentale is found extensively. The vegetation is mainly composed of dry deciduous elements, such as Carissa congesta, Hollarrhena pubescens, Lantana camara, Calycopteris floribunda, Woodfordia fruticosa, Grewia abutilifolia, Vitex negundo and species of Calotropis, Ziziphus, Cassia, Ixora, Acacia, Albizia, Terminalia and Crotalaria.
(b) Moist Mixed Deciduous Forests: This is the main type of forest found in Goa, covering more than half of the forest areas. In North Goa, this forest occurs around Tudal. Ordofind, Butpal, Molem, Codal, Abiche Gol near Valpoi, and Anmod ghat. Predominant species are Terminalia crenulata, T. belerica, T. paniculata, Lagerstroemia parviflora, Adina cordifolia, Albizia lebbeck, A. procera, Mitragyna parvifolia, Holoptelia integrifolia, Trewia nudiflora, Dillenia pentagyna, Semicarpus anacardium, Mallotus philippensis and Stereospermum colais.
(c) Secondary Moist Mixed Deciduous Forests: Trees found in this type of forest are knotty and of coppice origin. A few trees of primary origin are scattered. This type of forest is found mainly in areas of Kumeri cultivation and in other areas affected by biotic interferences. The main species found here are Terminalia crenulata, T. chebula, Adina cordifolia, Alstonia scholaris, Lannea coromandelica, Bombax ceiba, Careya arborea and Dillenia pentagyna.
(d) Sub-Tropical Hill Forests: These forests have formed due to Kumeri cultivation in the past. Syzygium cuminii and Cinnamomum verum are common here. Caryota urens is the most common palm in this type of forest. In the second storey, Strobilanthes callosus, Elaeagnus conferta and Capparis sp. are found.
IV) SEMI-EVERGREEN & EVERGREEN FORESTS
(a) Semi-Evergreen Forests: This type of forest occurs in between tropical evergreen and moist deciduous forests, and can be seen in Ambochegol, Molem, Butpal and Nadquem. Species include Artocarpus hirsutus, A. gomezianus, Calophyllum sp., Sterculia guttata, Kydia calycina, Lagerstroemia microcarpa, Pterospermum diversifolium, Garcinia indica, Diospyros montana and Macranga peltata.
(b) Lateritic Semi-Evergreen Forests: This type of forest is found on shallow, dry lateritic soils. Xylia xylocarpa is the prominent tree species with others such as Pterocarpus marsupium, Grewia tiliifolia, Terminalia paniculata, Schleichera oleosa, Careya arborea, Bridelia retusa and Strychnos nuxvomica.
(c) Evergreen Forests: This type of forest occurs in deep gorges and depressions and also along nallahs and streams in the Ponda-Amboli-Rambhat belt. The main species are Calophyllum calaba, Garcinia gummigutta, Canarium strictum, Lophopetalum wightianum, Myristica sp., Knemaat tenuata, Chroisophyllum acuminata, Palaquium ellipticum, Artocarpus gomezians, Diospyrus ebenum, Mangifera indica, Persea macrantha, Mimusops elengi, Hopea ponga, Olea dioica, Hydnocarpus pentendra, Syzygium cumini, Holigarna arnotiana, Litsea coriacea, Mallotus philippensis, Ficus sp. etc. Osmunda regilis, the royal fern, which is rare in peninsular India, can be found in this type of forest.