Long-term precipitation records from the extremely arid northern coast of Chile (18°S-30°S) were analysed to assess changes occurring at different time scales. Results are presented here along with a discussion on changes in the temperature and cloudiness regimes in order to offer a more comprehensive overview of the climate evolution in this extremely arid region. Apart from a significant influence of ENSO on the rainfall regime, characterized by a tendency for more frequent rainfall events during El Niño episodes, changes at the decadal time scale were identified in association with the Interdecadal Pacific Oscillation (IPO). Thus, the warm IPO-phase is associated with increased precipitation, while the opposite occurs during the cold IPO-phase. Changes occurring at the interannual and decadal time scales are superimposed on a long-term precipitation decline during the 20th century. Apart from the intensified dryness, the temperature records show a positive long-term trend resulting mainly from an abrupt warming in the mid-1970s, principally associated with a marked upwards shift of the minimum daily temperature, coinciding with the change from the cold to the warm phase of the IPO. However, the period following this step-like warming has been characterized by a persistent cooling trend, most evident in the maximum daily temperature, which is coherent with a negative trend in the sea surface temperature over a large oceanic region off the coast of northern Chile. In the northernmost region, this behaviour in the temperature regime was accompanied by a strong decrease in cloudiness since the 1970s. The negative trend in rainfall and the decrease in the total cloud cover are certainly important factors that could explain the coastal vegetation decline over the past decades in the coastal region north of 24°S.

Along the hyper-arid Chilean coastal desert between 30°S and 18°S the Loma vegetation undergoes a gradual transition from open shrubland to small isolated areas of a scarce plant cover. Floristic and physiognomic features allow a differentiation of five Loma formations, each of them characterized by a distinctive spectrum of plant communities. However, particularly in the northern section of the investigation area, numerous indications point to a strong vegetation decline including a deterioration of plant cover, reduction of the vitality of various taxa, probably also a local loss of some perennial species, and even a dieback of specific populations. These signs of a retrogression, which coincide with a regional disappearance of Guanaco herds in the coastal area between 20°S and 23°30'S, became apparent in the second half of the past century and were most likely provoked by recent climate change in the arid coastal region. Especially the decrease of rainfall frequency might have negative implications for the regeneration and preservation of plants. In addition, a strong reduction of cloudiness in the northernmost section affects plant growth due to further limitations in the water disposability. A projected sustained decline of rainfall is expected to continue endangering the surprisingly high floristic diversity of the sensitive ecosystem complexes in the coastal desert. Zusammenfassung: Entlang der perariden chilenischen Küstenwüste von 30°S bis 18°S verändert sich die Loma-Vegetation von offenen Strauchbeständen hin zu isolierten Pflanzenvorkommen geringer Deckung. Floristische und physiognomische Kriterien erlauben eine Untergliederung in fünf Abschnitte, die sich jeweils durch ein eigenes Spektrum an Pflanzengesellschaften auszeichnen. Allerdings belegen im Norden des Untersuchungsgebietes zahlreiche Merkmale eine Verminderung der Vitalität einzelner Sippen, den lokalen Verlust einiger perenner Taxa und sogar den Niedergang ganzer Populationen einzelner Arten. Dieser Vegetationsrückgang, der mit den Verlust von Guanaco-Herden aus der Küstenregion zwischen 20°S und 23°30'S einhergeht, zeichnet sich vor allem seit der zweiten Hälfte des letzten Jahrhunderts ab und ist mit großer Wahrscheinlichkeit auf Veränderungen im Klima der ariden Region zurückzuführen. Insbesondere die Abnahme der ohnehin bescheidenen Regenhäufigkeit dürfte sich negativ auf die Regeneration und den Erhalt der Pflanzen auswirken. Zudem beeinflusst ein Rückgang der Bewölkung im Norden der chilenischen Küstenwüste die Lebensbedingungen der Vegetation aufgrund weiterer Beschränkungen im Wasserhaushalt negativ. Die absehbare weitere Abnahme der Niederschläge wird die überraschend große Pflanzendiversität des höchst sensiblen Loma-Ökosystem-Komplexes auch in Zukunft bedrohen

La flora de los alrededores de Tocopilla está compuesta por 146 especies de plantas vasculares. Entre las formas de vida, las terófitas presentan el mayor número de especies en la flora (43%), pero están totalmente ausentes durante los años secos. Dos unidades de vegetación pueden ser identificadas: matorral desértico de Nolana peruviana, en las quebradas y laderas bajo 500 m de altitud, y matorral desértico de Eulychnia iquiquensis y Ephedra breana, en las laderas sobre 500 m. Se discuten algunos aspectos relativos a la flora y la relación entre el clima y la vegetación.

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