Rainfall reveals botanical treasure in the Chilean Atacama Desert

The Atacama Desert is one of the driest places on earth, and the flora has adapted to survive long drought periods, either as bulbs deep underground, or as seeds that can survive for decades without rain. Unusually, at the end of March 2015, some parts of the Atacama desert received 20mm of precipitation (close to the expected annual total), which produced damaging mud-slides in northern towns. We urgently made preparations to explore the region and find new seed collections that could be preserved at the INIA’s base seed bank with samples also to be duplicated at Kew’s Millennium Seed Bank at Wakehurst Place in Sussex. 

Why is the flora of the Atacama Desert so special?

The Atacama Desert extends from the north of Chile’s mediterranean climate zone, at about latitude 29°S, into southern Peru, and is isolated from the rest of the continent by the prominent Andean mountain chain dividing Chile from her immediate neighbours. The region has not always been desert: following  pulses of dry and humid climate during the Pleistocene, it is thought that the current arid climate became established during the Holocene period, approximately 10,000 years ago (Maldonado & Rosas, 2008). The flora of the Chilean Atacama region now has around 1,000 native vascular plant species, of which 54.3% are endemic according to Squeo et al. (2008). Plant distributions are often quite restricted within the region; León-Lobos et al. (2011) reported that a third (31%) of the endemics in the Atacama are found within a single administrative region and therefore intensive and well-prepared fieldwork is needed to locate and collect from these species.

What are the threats to the flora?

The Atacama is extensive and has a small human population, so why would the flora require any particular protection? In fact, the long history, since the 18th century, of exploitation of minerals from northern Chile, initially for bird-derived guano fertiliser and more recently for copper, has left a legacy of mines, tailings, and access roads and railways which have disturbed the fragile surface of the desert. More recent development of wind turbines and solar installations to help meet Chile’s target to generate 20% of its energy from renewable sources by 2020, are also having a cumulative impact on parts of the desert, which has formal protection (National Parks or National Reserves) in only 1.8% of its land area (Squeo et al 2008). Faced with additional threats including grazing, agriculture, road and tourism developments, Kew and INIA have committed to seed-banking to help preserve samples of endemic flora for future generations. These collections will also help Kew towards its target to preserve seed from 25% of the world’s bankable plant species (see link to 2020 Strategic Outputs below).

What have we learnt about saving seeds from this unique flora?

As seed collectors, we have to plan ahead and be prepared to mount expeditions in response to unusual rainfall. We take advantage of the capacity for desert plants, especially the annuals, to complete their life cycle rapidly and to shed copious seed which can be collected without harming their populations. Gutierrez (2008) actually reports that the soil seed bank in Fray Jorge National Park, on the southern edge of the Atacama region, was replenished by over ten times after a desert flowering event in 1991-92, and our Millennium Seed Bank Partnership standards limit collection to no more than 20% of seed available at that time, to ensure that the soil seed bank will not be depleted.

Scouting trips at flowering times are valuable opportunities to identify target species, to map populations, and to plan subsequent seed collecting fieldwork. However, one cannot predict with certainty how every population responds to specific conditions, and it remains essential for seed collectors to be well trained, well informed, and fully flexible to respond to conditions that they encounter in the field, in order to successfully make these important seed collections.