Abstract
Concerns about the negative effects of declining agricultural biodiversity due to modern agricultural practices and climatic constraints in various parts of the world, including Iran, on the sustainability of agricultural ecosystems are increasingly growing. However, the historical knowledge of temporal and spatial biodiversity is lacking. To determine the value and trend of crop diversity in Iran, we used biodiversity indices based on the area under rainfed and irrigated crops and total cropland area from 1991 to 2018. There were large fluctuations in the amount of cultivated area in the past 30 years, peaking around 2005 to 2007 with about 13.1 million cultivated hectares. However, no general trend in increase or decrease of total cultivated land was shown. The crop species diversity of irrigated cropland was higher than the rainfed and total cropland. The Shannon diversity index showed a constant trend with a negligible slope, but species richness was increased, which was related to the rise in the area of some crop species in recent years. The area of wheat and barley had a significant impact on crop diversity, so Shannon diversity index reduced with their dominance. Overall, this study revealed that the Iranian agricultural system relies on wheat and barley. We warn that by increasing the area of these crops and the prevalence of monoculture, the probability of damage from external factors such as sudden weather changes or the spread of diseases will increase, leading to instability and production risks in the future.
Highlights
Producing food, feed, fiber and fuel for a growing population is a major challenge [1, 2] and climate change can have a negative impact on it, thereby affecting nutrition and human health and future food security [3, 4]
The results of this study showed that the total cropland area was almost constant trend with a negligible slope during the last three decades
Due to low average annual precipitation and the nonuniformity of annual precipitation distribution in Iran [2, 73], only crops such as wheat, barley and chickpea are grown in rainfed cropland, while in irrigated cropland, there is more crop diversity and crop species richness
Summary
Producing food, feed, fiber and fuel for a growing population is a major challenge [1, 2] and climate change can have a negative impact on it, thereby affecting nutrition and human health and future food security [3, 4]. Diverse agroecosystems with higher resilience to climate change [7] and different types of risks such as droughts, floods, frost, weed or pest infestation, input supply risks, price and yield risks, and other types of risks [8] will continue to produce nutritious and healthy food and provide ecosystem services [9–11]. This means that crop diversification increases the capacity of agroecosystems and provides protection against environmental variability as different crops respond differently to change [7]. Crop diversification in agroecosystem causes an increase in efficiency and productivity of resources and reduces risks [12, 13]
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