Antigua and Barbuda's geography: low islands that drink the sea

How three islands make up one small state

The state is two inhabited islands and one rock, spread along the eastern arc of the Leeward Islands where the Atlantic meets the Caribbean Sea. Antigua carries the capital, the airport and almost all of the people. Barbuda lies to the north, 40 kilometres away by Britannica's measure and 48 by the Wikipedia geography, with its one village, Codrington, on a lagoon on the west coast. Redonda, uninhabited, lies to the south-west of Antigua. The country's maritime boundaries meet those of Anguilla, Saint Barthélemy, Saint Kitts and Nevis, Montserrat and Guadeloupe. Guiana Island and Long Island, just off Antigua, are the biggest of the offshore islets.

The published figures for the islands do not agree, and the differences are worth printing because each comes from a different measurement:

Redonda is a steep rock with very little level ground. Britannica notes phosphate deposits on it, and they were mined until 1929; the island has had no inhabitants since. Under the Redonda Annexation Act it counts as part of the parish of Saint John on Antigua, the most populous of the six parishes.

The record for the whole state gives 440 km². The sea is far larger: the country claims an exclusive economic zone of 110,089 km², because the three islands are spread out across it.

Why Antigua's south-west stands higher

Antigua is low. Limestone has shaped more of it than volcanic activity has, and the Wikipedia geography describes three zones: limestone in the north-east and north-west, a central plain of clay between them, and a knot of hills of volcanic origin in the south-west. Those hills, the Shekerley Mountains, hold the country's highest point. Boggy Peak, the remnant of a volcanic crater, rises to 402 metres in Wikipedia's figure and 405 metres in Britannica's. It was renamed Mount Obama in 2008; Wikipedia records the name as used until 2016, while Britannica still gives Mount Obama with Boggy Peak as the former name.

The hills also mark a language boundary. Wikipedia's account of Antiguan and Barbudan Creole notes that the Shekerley Mountains cut the southern villages, known as Round South, off from the centre of population, which is why South Antiguan Creole is only partly understood by speakers from the rest of the island.

Most people live on the Central Plain that runs from St. John's on the north-west coast towards English Harbour in the south. The coastline is heavily indented, with bays, headlands, lagoons and natural harbours, and reefs and shoals ring the island on every side. Britannica names Parham and English Harbour as sheltered anchorages and St. John's as the deepwater port, where ships drawing up to 10.5 metres can come in. UNESCO's description of English Harbour explains why the navy chose it: deep, narrow bays surrounded by high ground that gave shelter from hurricanes.

Barbuda is a different kind of island. It is coral limestone, flat and wooded, with a raised plateau in the east called the Highlands and a large lagoon along the west. The Barbuda entry on Wikipedia puts the hills of the Highlands at up to 38 metres and the geography article gives the plateau's northern edge as 44.5 metres, while Britannica names Lindsay Hill at 44 metres. The plateau is cut by sinkholes and caves. Darby Cave, about three and a half miles north-east of Codrington, is a sinkhole more than 300 feet across and around 70 feet deep with palms and ferns growing at its floor.

Where Antigua gets its water

Neither island has an adequate supply of fresh groundwater, and Antigua has no rivers. The Organization of American States studied the problem after Hurricane Georges, and its drought assessment of April 2001 gives the basic numbers. Mean annual rainfall was 40.98 inches on Antigua and 34.74 inches on Barbuda, and the report treats a year with less than 80% of the average as a meteorological drought. Antigua had eight such years between 1960 and 2000, and Barbuda fell below its threshold on ten occasions between 1965 and 2000.

The worst of them was 1983, when the Coolidge meteorological office recorded 22.31 inches. At that time the Potworks Dam supplied more than half the water used on Antigua, so supply rose and fell with the rain. Households went without piped water for months, hotels trucked water in, and the 268Weather blog later recalled that water had to be barged from Dominica. The government's answer was desalination, which the OAS report of 2001 put at 62% of Antigua's water consumption, and many hotels installed their own reverse osmosis plants.

Desalination has reduced the problem without ending it. In August 2015, after about two years of drought, the Antigua Public Utilities Authority reported that every surface catchment had fallen below extraction level. The island was producing about 5.5 million imperial gallons of potable water a day against a demand of about 8 million, and the daily mix was 83% desalinated water and 17% groundwater. In a normal year, by the same account, 57% came from the sea, 28% from surface catchments and 15% from wells. January to July 2015 was the driest such period on the island's records, which reach back to at least 1928.

Barbuda remains dependent on groundwater as its main source of supply, according to the OAS report, and notes that sand mining has damaged its main aquifer. It also names overgrazing by goats as perhaps the primary factor in the country's vulnerability to drought, since bare soil erodes fastest in dry spells.

How the trade winds set the climate

The climate is moderated by fairly constant north-east trade winds, which blow at 30 to 48 kilometres an hour, and humidity is generally low. Temperatures average about 27 °C. Britannica gives an average of about 25 °C in January and 28 °C in August, with summer highs reaching 32 °C. The highest temperature on record is 34.9 °C, measured at St. John's on 12 August 1995. The coolest months are December to February and the wettest are September to November, although the amount of rain varies widely from one season to the next.

The Wikipedia geography attributes the thin rainfall to the islands' low elevation, and Britannica records that Barbuda, flatter still, receives less rain than Antigua.

The Wikipedia country article classifies the climate as tropical savanna, with pockets of tropical monsoon climate in Antigua's wetter south-west, and Barbuda's entry calls its climate tropical marine, with little change in temperature through the year.

Hurricanes arrive on average about once a year between July and October, by the Wikipedia geography's reckoning. Hurricane Luis damaged Barbuda badly in 1995, and Irma in 2017 was of another order.

What Hurricane Irma did to Barbuda

Irma crossed the northern coast of Barbuda at its peak intensity early on 6 September 2017, a Category 5 storm. A weather station on the island measured a gust of 160 miles an hour and a minimum pressure of 916.1 millibars, and downed lines then cut the island off for hours. Official estimates, as reported by the Caribbean Investigative Journalism Network, found 95% of the island's structures damaged or destroyed, the hospital, the schools and both hotels among them. UNICEF reported one death, a two-year-old boy; the Wikipedia account of the storm records three storm-related deaths on the island. NASA's Landsat images turned from green on 27 August to brown on 12 September, as the wind stripped vegetation and salt spray dried out the leaves that were left.

With Hurricane Jose following almost the same track, the government urged residents to leave and then ordered it. UNICEF reported on 8 September 2017 that up to two thirds of Barbuda's roughly 1,500 residents were expected to cross to Antigua by the end of that week, many on pleasure boats normally used for day trips. A mandatory evacuation followed on 9 September. Most residents had returned by February 2019, according to the Barbuda entry on Wikipedia.

The damage was measured afterwards. An assessment carried out with the United Nations, the European Union, the Caribbean Development Bank and the Eastern Caribbean Central Bank put Barbuda's recovery needs at US$222.2 million in 2017, of which US$79.6 million was for housing: 45% of houses were left uninhabitable and 28% needed replacing entirely. Antigua, outside the strongest winds, lost roofs, fences, power lines and trees.

What lives in Codrington Lagoon

Most of Barbuda's west coast is one national park, Codrington Lagoon, which the Caribbean Birding Trail describes as stretching about 16.5 miles. It has been a Wetland of International Importance under the Ramsar Convention since 2005, the only one in the country. A narrow strip of sand separates it from the sea along a beach known as 17-Mile Beach.

The lagoon's mangroves hold a large nesting colony of magnificent frigatebirds, the national bird. Counts differ. The Caribbean Birding Trail puts it at about 2,500 pairs; the Wikipedia account of Irma repeats the estimate of 2,500 nesting pairs, and a local guide quoted in Canadian Geographic said more than 5,000 birds nest there. The birds court and nest between September and April, the males inflating red throat pouches. Brown boobies loiter in the colony and laughing gulls nest on the sand beneath the mangroves. Irma's storm surge flooded the lagoon in 2017.

Barbuda is also the only home of the Barbuda warbler, a small bird that numbered fewer than 2,000 before Irma and was found to have come through the storm largely intact. The Antiguan racer, a snake found on both islands, now occupies 0.1% of its historical range. European fallow deer live on Barbuda and on Guiana Island and nowhere else in the eastern Caribbean.

The lagoon is also where Barbuda's geography meets its politics. The Global Legal Action Network, which supports Barbudan claimants in several cases, records that the sandbar enclosing the lagoon was breached, and that a golf course and resort have been built on the protected wetland; its submissions to the Ramsar Secretariat in 2020 and March 2022 describe the harm to the site. The government's case is the subject of Antigua and Barbuda: politics.

How much of the land is still forest

Britannica points to the absence of mountains and forests as what sets Antigua apart from the other Leeward Islands. The Wikipedia economic history explains the cause: the sugar estates cleared the rainforest for cane, and the timber went to building and repairing ships. Forest covered 8,120 hectares in 2020, about 18% of the land, down from 10,110 hectares in 1990. A land-use survey of 2011 gave arable land as 20.5% of the total, permanent pasture 9.1% and forest 22.3%, a different measure from a different year.

What remains is concentrated in the Shekerley Mountains, where the Wallings forest is protected. Clearing trees for crops also makes the drought problem worse, because rain runs off bare slopes before it can soak in, a point the CIA's environmental summary, reproduced in the Wikipedia geography, makes about water management.