Maui has literally hundreds of beaches. Many of these are hidden away in wild, inaccessible places and never see a single human footprint. Landscape photographers and beach ecologists yearn for these beautiful and untouched stretches of sand and rock, and willingly risk life-and-limb clambering over cliffs and crawling through disintegrating lava tubes to discover them.
Then there’s the Urban Beach. Families with young children, less sure-footed seniors (like myself), early morning beachcombers, and those folks who seek good karma through tan maintenance all treasure the Urban Beach.
Tree Heiliotrope (Tournefortia argentea) and Ironwood trees (Casuarina equisetifolia) at Kanaha Beach, located east of the international airport in Kahului.
For reasons meteorological and geological, the leeward side of Maui (my side of the Island) has more than its fair share of urban beaches. The only prerequisite for this type of beach is that it is located inside the city limits. The kama’aina islanders all have their favorites that they tell their friends about, and they usually have at least one whose whereabouts they keep for themselves.
Coconut Palms (Cocos nucifera) sink their roots into the sand just above the high-tide line on a north Kihei beach.
Humans are not the only inhabitants of urban beaches: trees, shrubs, and vines all crowd the sea cliffs, sand berms, and dunes right down to the waterline. Many plant species that inhabit the Strand Vegetation Zone are able to tolerate salt spray and not-so-gentle prevailing winds, and even dip their roots in saltwater-saturated sand and coral debris. The sturdy root systems and ground-hugging habits of the shrubs, grasses, vines, and perennial herbs of this vegetation zone stabilize drifting sand and coral debris to form elevated berms and stable dune fields where soils can form that eventually will support other less-hardy plant species and provide homes for birds and insects.
These plant species also prevent beach erosion by trapping and holding in place vast amounts of sand, coral and plant debris, and soil. Some of the beach deposits act as barriers to the seaward flow of freshwater streams, forming back-beach wetlands that serve as nesting grounds for resident and migratory birds, and host several species of freshwater fish, amphibians, and aquatic insects.
The Kiawe (Prosopis pallida), related to acacia trees, is the only coastal dry forest tree that forms a true canopy. Every tree in this photo (except the coconut palms at bottom left) is a Kiawe.
Unfortunately, non-native invasive species like the Kiawe are all too good at competing with and edging out the native species, and almost none of the colorful shrubs, herbaceous vines, and trees are native to the Islands.
This photograph taken under the canopy of a dense thicket of Kiawe trees shows how efficient Prosopis pallidus is at crowding out all other plant species, with the exception of a few sorry patches of grass.
Fortunately there are still quite a few urban beaches on Maui where aggressive invaders like the Kiawe are not well established. Here there is more of a variety of plant life: Endemic (evolved in Hawai’i) and indigenous (colonized the Islands before the arrival of humans) species have a more open environment to establish themselves alongside the inevitable alien species.
A thick carpet of ‘Aki ‘Aki (Sporobulus virginicus), perennial grass that thrives on hot sun and salt spray, has stabilized the coarse sand and coral debris of this Kihei beach. Viney plants like Beach Morning Glory, and coconut palms and ironwood trees are well spaced and grow tall in the sandy soil anchored by the grass mat.
Beach Morning Glory (Ipomoea pes-caprae) is a salt-tolerant creeping vine whose seeds float and are unaffected by salt water, enabling them to be dispersed by wave action.
Ipomoea pes-caprae is often associated with ‘Aki ‘Aki, a perennial salt-tolerant grass. As shown in this photo, the grass and vines grow in amongst one another, forming a dense vegetation mat that can stabilize even the coarsest beach sand and coral rubble.
Its long runners and sturdy root system make the Beach Morning Glory a primary dune stabilizer.
Tree Heliotrope (Tournefortia argentea) and Beach Naupaka (Scaevola taccada) are two of the most common species found on Maui’s urban beaches. Though both these plants are considered invasive and “weedy” (NOT my term!), they both are considered effective at erosion control. Beach Naupaka is variously classified as “native” to Hawai’i or as “indigenous”. Tree Heliotrope (“Naupaka Kahakai” in Hawaiian) was introduced to the Islands in the 1850s. These shrubs can quickly colonize an open beach very quickly due to the ability of their branches send out rootlets when they come in contact with any substrate, no matter how poor the soil. Their seeds are resistant to salt water and float readily, enabling them to be dispersed far from the parent plant; however, they require fresh water to germinate, hence their preference for sand dunes and berms not completely saturated with salt water.
Tree Heliotrope (Tournefortia argentea) perched on a small stabilized sand dune, Kanaha Beach, Kahului.
Kiawe, Tree Heliotrope (center), and Beach Naupaka (sprawling, lighter colored shrub in bottom-right corner of photo) crowd each other on a north Kihei beach.
A Tree Heliotrope in bloom, north Kihei.
A Beach Naupaka blossom. Note the “half-flower” and green seed-bearing fruit.
The “ground-hugging” habit of Beach Naupaka. Tree Heliotrope generally has a more erect habit and possesses a tree-like in its most mature state.
There are very few truly “native” species of plants to be seen on Maui’s urban beaches; however, several threatened and endangered native species are being re-introduced to the coastal ecosystem through the combined efforts of private citizens, local and national conservation groups, and county and state organizations whose functions include stewardship of Hawaii’s botanical heritage. Two such species are being re-introduced to the berms and stabilized dune fields of Kanaha Beach in Kihei as part of Maui County’s numerous ongoing beach-restoration projects: ‘Ihi (Portulaca molokiniensis) and ‘Ohai (Sesbania tomentosa).
‘Ohai (Sesbania tomentosa) growing on a stabilized dune field, Kanaha Beach, Kihei.
‘Ihi (Portulaca molokiniensis), a rare native succulant plant, Kanaha Beach, Kihei.
Tags: Aki Aki, Beach Naupaka, beach plant life, Casuarina equisetifolia, ironwood, Maui's beaches, naupaka, Portulaca molokiniensis, Sesbania tomentosa, Sporobulus virginicus, strand vegetation zone, Tournefortia argentea, Tree Heiliotrope
