Science Snippets: Can farming actually save threatened species?

Christie Craig, the ICF/EWT African Crane Conservation Programme

As human development and global change accelerate, natural ecosystems are under immense and ever-growing pressure. In some cases, ecosystems are altered to such an extent that they can be considered novel. Intensively farmed areas are an example, and these novel ecosystems affect biodiversity. As conservation biologists, we anticipate this would spell disaster for wildlife, particularly threatened species, but this isn’t always true.

We have seen this in the case of South Africa’s National Bird, the Blue Crane (Anthropoides paradiseus). In the 1990s, alarms were raised as this species was declining rapidly in their natural range, the eastern grasslands and the Karoo, due to grasslands being degraded and transformed for agriculture and forestry and other threats such as poisoning and powerline collisions. Interestingly, however, on the other side of the country, in the Western Cape wheatlands, Blue Cranes responded to agricultural transformation in a remarkably different way. In the early 1900s, when people began clearing fynbos (generally unsuitable habitat for Blue Cranes), Blue Cranes started to move into the Western Cape. Since then, the population has boomed in this area. Today, 50% of all Blue Cranes in the world are found in this novel ecosystem.

Conservationists were concerned because it is challenging to conserve wildlife in highly transformed landscapes like this. We have seen Blue Crane numbers decline rapidly once before, and we were concerned that this could happen again if something shifted in the Western Cape wheatlands. Intensively farmed landscapes are dynamic and influenced by social factors such as farmers’ decisions, politics, economics, and climate change. In modern conservation, many are moving away from crisis management and taking a ‘fighting fires’ approach by being more proactive and foreseeing risks to prevent species declines before they happen and to maintain conservation success. With this in mind, the African Crane Conservation Programme set up a PhD project to investigate the Blue Crane’s conservation status, specifically focusing on understanding threats in the Western Cape wheatlands.

PhD candidate & Western Cape Field Officer Christie Craig has spent the last four years conducting this research and is in the process of wrapping up her thesis. Bringing all these data together, we now have a clearer picture of the state of the Blue Crane population. Over the last 30 years, we have seen an overall recovery in Blue Crane numbers, with the current national estimate obtained from aerial surveys at 44,500 Blue Cranes, which is 44% higher than the last estimate in 2002. This recovery was largely due to increases in the Western Cape wheatlands in the 1990s and early 2000s, as shown by citizen science data, i.e. Coordinated Avifaunal Roadcounts. Aerial surveys have also shown increased numbers in KZN, thanks to continued conservation action. However, the Blue Crane numbers in the grasslands are still a small remnant of what they used to be. Looking at the South African Bird Atlas Project data, we see changes in Blue Crane reporting rates, which tell us how many cranes there are. These data show that several areas of the eastern grasslands no longer have cranes, compared to the 1980s (in red, Figure 1). We hope Blue Crane numbers will recover to their full potential in the grasslands with continued conservation.

The Blue Crane’s adaptation to wheat and pasture agriculture in the Western Cape has been their saving grace and aided their recovery. However, we have some concerns that this population is no longer thriving. Analysis of citizen science data shows that the population trend changed from positive to negative in 2010, and since then, Blue Crane counts have declined by 22% in the Overberg. If this decline is sustained, we could see the national population decline by an estimated 53% over the next 37 years. We do not know whether these declines will continue at this stage, and we are monitoring the population carefully. We cannot pinpoint a single reason for this decline, but we know from research that Western Cape breeding success is lower than it used to be and lower than the Blue Cranes in the Karoo and grasslands. In the Karoo and grasslands, EWT field workers have documented an average fledgling rate of 1.01 chicks/pair (95% confidence intervals = 0.82-1.24) in the grasslands and 1.02 chicks/pair (95% CI = 0.76-1.35) in the Karoo. Western Cape Blue Cranes only fledge an average of 0.64 (95% CI 0.42-0.95) in the Swartland and 0.81 fledglings/pair (95% CI 0.57-1.12) in the Overberg. The agricultural landscape can be challenging for breeding Blue Cranes as they attempt to breed in the dry season, when wheat is being harvested, and there is a lot of disturbance in fields. Other threats to Blue Cranes, once they fledge, include powerline collisions and poisoning.

Map showing Blue Crane reporting rates in SABAP1 vs SABAP2

Figure: Comparison of Blue Crane reporting rates in SABAP1 vs SABAP2, indicating Quarter Degree Grid Cells (QDGCs) where cranes have never been recorded (never), where they were recorded in SABAP1 but weren’t in SABAP2 (absent) and vice versa (new), and where they were recorded in both projects, the direction of reporting rates from SABAP1 to SABAP2 (down, level or up). QDGCs with fewer than four cards in either project are indicated in blue.

Now that we have data on the population trends and threats, we will feed this directly into conservation action. The first step is to develop a conservation plan. We will host a workshop in the coming months, bringing together all the stakeholders and experts to develop a conservation planning document and implementation strategy.

This work is kindly sponsored by Neuwied Zoo, Jacksonville Zoo, Safari West, Nashville Zoo, and the Leiden Conservation Foundation. The PhD research was funded by the Leiden Conservation Foundation, Eskom & the Hall-Johnson Fellowship.